1 00:00:03,000 --> 00:00:04,467 NARRATOR: Helike, 2 00:00:04,467 --> 00:00:08,066 one of the greatest ports of classical Greece. 3 00:00:08,066 --> 00:00:12,467 This entire city, just like fabled Atlantis, vanishes 4 00:00:12,467 --> 00:00:16,800 to all but legend for over 2,000 years. 5 00:00:16,900 --> 00:00:20,166 Now, pioneering archaeologists believe they have 6 00:00:20,166 --> 00:00:23,734 unearthed the ruins of this ancient metropolis. 7 00:00:29,266 --> 00:00:30,000 NARRATOR: The investigation into Helike's fatal 8 00:00:30,000 --> 00:00:31,734 NARRATOR: The investigation into Helike's fatal 9 00:00:31,800 --> 00:00:36,266 final days inspires cutting-edge experiments 10 00:00:36,266 --> 00:00:39,634 to test the true cause of the city's disappearance. 11 00:00:45,100 --> 00:00:47,533 NARRATOR: Does a single wave devastate Helike? 12 00:00:50,533 --> 00:00:54,734 Or does the earth itself consume its sacred stone structures? 13 00:00:54,800 --> 00:00:56,800 [thunder crashes] 14 00:00:56,900 --> 00:01:00,000 And could Helike's rediscovery lead the way to 15 00:01:00,000 --> 00:01:00,166 And could Helike's rediscovery lead the way to 16 00:01:00,233 --> 00:01:04,166 the most famous lost city of all, Atlantis? 17 00:01:06,867 --> 00:01:09,066 To solve these mysteries, 18 00:01:09,066 --> 00:01:13,066 we digitally reconstruct this bustling ancient capital. 19 00:01:14,533 --> 00:01:16,800 We rediscover the lost monuments 20 00:01:16,900 --> 00:01:19,367 once worshiped by the city's residents 21 00:01:21,166 --> 00:01:25,333 and crack the mystery of why Helike is hidden for so long 22 00:01:26,867 --> 00:01:30,000 to unlock the true story of Greece's real-life Atlantis. 23 00:01:30,000 --> 00:01:31,734 to unlock the true story of Greece's real-life Atlantis. 24 00:01:44,166 --> 00:01:48,533 50 miles from Athens is Greece's Peloponnese peninsula. 25 00:01:50,367 --> 00:01:53,467 Somewhere along this coast lie the remains of Helike, 26 00:01:55,066 --> 00:01:57,433 one of the great cities of ancient Greece. 27 00:02:00,266 --> 00:02:03,066 Homer's Iliad describes its proud people 28 00:02:03,100 --> 00:02:05,634 going into battle under King Agamemnon 29 00:02:05,734 --> 00:02:07,333 during the siege of Troy. 30 00:02:09,367 --> 00:02:14,000 2,400 years ago, the city disappears overnight. 31 00:02:20,100 --> 00:02:24,266 Ancient texts describe a walled city-state that 32 00:02:24,266 --> 00:02:27,634 thrives as Greek culture and military might dominate 33 00:02:27,634 --> 00:02:28,800 the Mediterranean. 34 00:02:31,367 --> 00:02:34,166 Its people worship the almighty Poseidon 35 00:02:34,867 --> 00:02:37,634 and construct a temple and sanctuary in his honor, 36 00:02:40,066 --> 00:02:43,266 as well as a giant bronze statue of the sea god. 37 00:02:46,533 --> 00:02:48,734 In 373 BCE, 38 00:02:48,800 --> 00:02:51,634 a disaster destroys the city, 39 00:02:51,634 --> 00:02:55,734 and like Atlantis, Helike disappears. 40 00:02:56,867 --> 00:03:00,000 What happens to the city, and where is it today? 41 00:03:00,000 --> 00:03:00,900 What happens to the city, and where is it today? 42 00:03:06,100 --> 00:03:09,533 One of archaeology's greatest quests is to find Helike 43 00:03:11,634 --> 00:03:15,467 and unravel the mystery of the city's fatal final days. 44 00:03:18,000 --> 00:03:19,467 Dora Katsonopoulou 45 00:03:19,467 --> 00:03:21,166 has searched longer than any 46 00:03:21,166 --> 00:03:25,367 other investigator to unearth this legendary metropolis. 47 00:03:37,000 --> 00:03:39,800 NARRATOR: Luckily, she has help. 48 00:03:39,900 --> 00:03:42,367 An ancient eyewitness leaves clues to 49 00:03:42,433 --> 00:03:44,533 the location of the great lost city. 50 00:03:47,500 --> 00:03:51,166 He spots Helike's ruins, five centuries after 51 00:03:51,233 --> 00:03:53,266 its destruction, 52 00:03:53,333 --> 00:03:56,333 and records the distance to two local landmarks. 53 00:03:58,500 --> 00:04:00,000 First is the still-standing city of Aigion to the west. 54 00:04:00,000 --> 00:04:02,900 First is the still-standing city of Aigion to the west. 55 00:04:18,867 --> 00:04:22,066 NARRATOR: He also states the ruins are 30 stadia, 56 00:04:22,100 --> 00:04:26,634 3 miles from a place known as the Cave of Herakles. 57 00:04:38,100 --> 00:04:40,734 NARRATOR: Dora measures from the two fixed points. 58 00:04:47,867 --> 00:04:50,734 NARRATOR: Helike's search area is today 59 00:04:50,800 --> 00:04:53,333 roughly 2/3 land and 1/3 sea. 60 00:04:55,100 --> 00:04:56,967 It means the city could now lie 61 00:04:56,967 --> 00:05:00,000 underwater in the nearby Gulf of Corinth. 62 00:05:00,000 --> 00:05:00,100 underwater in the nearby Gulf of Corinth. 63 00:05:13,166 --> 00:05:14,634 NARRATOR: An eyewitness reports 64 00:05:14,734 --> 00:05:17,266 Helike lies underwater 65 00:05:17,333 --> 00:05:20,233 150 years after its destruction. 66 00:05:24,166 --> 00:05:28,367 The sacred bronze statue of Poseidon still stands, 67 00:05:28,433 --> 00:05:30,000 holding a half-horse, half-fish mythical beast, 68 00:05:30,000 --> 00:05:32,533 holding a half-horse, half-fish mythical beast, 69 00:05:32,634 --> 00:05:33,734 the hippocamp. 70 00:05:35,600 --> 00:05:39,166 It snags on fishing nets passing above. 71 00:05:39,166 --> 00:05:40,634 Four hundred years later, 72 00:05:40,734 --> 00:05:44,066 another eyewitness describes the city. 73 00:05:44,066 --> 00:05:45,734 Badly corroded from salt, 74 00:05:46,700 --> 00:05:50,467 it remains a well known local landmark. 75 00:05:50,533 --> 00:05:53,734 Does Helike lie hidden beneath the water today? 76 00:05:56,867 --> 00:05:59,467 Starting in the 1960s, 77 00:05:59,533 --> 00:06:00,000 guided by the ancient accounts, 78 00:06:00,000 --> 00:06:01,634 guided by the ancient accounts, 79 00:06:01,634 --> 00:06:04,634 Dora and others search for the lost city. 80 00:06:06,467 --> 00:06:09,066 Experts use sonar, 81 00:06:09,100 --> 00:06:10,900 divers, 82 00:06:11,000 --> 00:06:14,467 and undersea drills to systematically probe 83 00:06:14,467 --> 00:06:17,166 the seabed of the Gulf of Corinth. 84 00:06:18,367 --> 00:06:20,734 They return empty-handed. 85 00:06:27,734 --> 00:06:30,000 NARRATOR: Dora refuses to give up on the hunt for Helike. 86 00:06:30,000 --> 00:06:31,166 NARRATOR: Dora refuses to give up on the hunt for Helike. 87 00:06:32,600 --> 00:06:36,467 She re-examines the ancient eyewitness's description. 88 00:06:36,467 --> 00:06:39,634 [speaking foreign language] 89 00:06:58,600 --> 00:07:00,000 [speaking foreign language] 90 00:07:00,000 --> 00:07:00,634 [speaking foreign language] 91 00:07:02,867 --> 00:07:04,634 NARRATOR: The Greek word "poros" 92 00:07:04,634 --> 00:07:06,800 means a narrow stretch of water. 93 00:07:08,000 --> 00:07:10,266 Other experts assume this stretch of 94 00:07:10,266 --> 00:07:12,533 water must be the Gulf of Corinth. 95 00:07:14,367 --> 00:07:17,700 Dora thinks if the eyewitness spots the statue there, 96 00:07:17,700 --> 00:07:19,467 he would use its proper name, 97 00:07:19,467 --> 00:07:20,634 the Gulf of Corinth. 98 00:07:21,734 --> 00:07:25,467 It must lie beneath a different stretch of water. 99 00:07:40,066 --> 00:07:42,467 NARRATOR: If Dora's theory is correct, 100 00:07:42,533 --> 00:07:44,467 she'll disprove some of the world's 101 00:07:44,467 --> 00:07:46,166 greatest archaeologists. 102 00:07:47,867 --> 00:07:51,900 The problem is the lagoon has long since disappeared. 103 00:07:53,266 --> 00:07:56,066 Where might the lost city lie today? 104 00:07:57,533 --> 00:07:59,800 And can its ruins reveal what 105 00:07:59,900 --> 00:08:00,000 happens on Helike's fatal final day? 106 00:08:00,000 --> 00:08:03,233 happens on Helike's fatal final day? 107 00:08:15,734 --> 00:08:20,800 NARRATOR: The great city of Helike is destroyed in 373 BCE. 108 00:08:22,867 --> 00:08:25,266 Its ruins are last seen underwater 109 00:08:25,333 --> 00:08:27,734 nearly 2,000 years ago. 110 00:08:29,100 --> 00:08:33,166 Fresh analysis of ancient eyewitness reports suggests 111 00:08:33,166 --> 00:08:35,734 the city may not be lost beneath the sea. 112 00:08:37,166 --> 00:08:40,040 It may lie under an inland lagoon that has vanished. 113 00:08:40,040 --> 00:08:41,166 It may lie under an inland lagoon that has vanished. 114 00:08:42,100 --> 00:08:44,734 [engine revving] 115 00:08:44,800 --> 00:08:47,634 Dora's team searches for the lost lagoon 116 00:08:47,734 --> 00:08:48,900 and the city beneath. 117 00:08:50,166 --> 00:08:52,533 They drill 99 boreholes in 118 00:08:52,533 --> 00:08:55,634 the region outlined by the ancient eyewitness account. 119 00:08:57,467 --> 00:09:00,867 Lead Geologist Ioannis Koukouvelas examines 120 00:09:00,867 --> 00:09:02,634 mud cores from the boreholes. 121 00:09:26,467 --> 00:09:29,166 NARRATOR: The green tint dates this sample layer 122 00:09:29,166 --> 00:09:33,166 to 2,400 years before the present day, 123 00:09:33,166 --> 00:09:35,734 the time of Helike's great disaster. 124 00:09:38,000 --> 00:09:40,040 The layer also contains the smoking gun 125 00:09:40,040 --> 00:09:40,433 The layer also contains the smoking gun 126 00:09:40,500 --> 00:09:44,266 the team is searching for -- signs of human occupation. 127 00:09:55,000 --> 00:09:56,800 NARRATOR: The ceramics could be from Helike. 128 00:09:58,533 --> 00:10:01,900 The team excavates around the most promising boreholes. 129 00:10:07,000 --> 00:10:08,900 Beneath 10 feet of mud, 130 00:10:08,900 --> 00:10:10,040 they uncover the remains of an ancient dwelling. 131 00:10:10,040 --> 00:10:12,467 they uncover the remains of an ancient dwelling. 132 00:10:12,467 --> 00:10:17,533 Inside, they find a small clay sculpture of a female idol, 133 00:10:19,634 --> 00:10:21,967 fragments from a shattered vase, 134 00:10:23,467 --> 00:10:27,900 and Greek coins, one featuring a pair of dolphins. 135 00:10:29,100 --> 00:10:31,867 The finds reveal a settlement that dates to 136 00:10:31,900 --> 00:10:34,467 the 4th century BCE. 137 00:10:34,467 --> 00:10:36,734 If this is ancient Helike, 138 00:10:36,800 --> 00:10:39,634 where is the evidence for the lost lagoon? 139 00:10:40,467 --> 00:10:44,100 A clue lies 5 feet above the ruins -- 140 00:10:44,100 --> 00:10:46,066 a dark layer of sediment. 141 00:10:49,634 --> 00:10:53,634 The finds suggest Dora's controversial theory that Helike 142 00:10:53,734 --> 00:10:57,734 lies under a lost lagoon could be correct. 143 00:10:57,734 --> 00:10:59,467 But the team needs proof 144 00:10:59,467 --> 00:11:02,967 the dark layer corresponds to the bed of an ancient sea lake. 145 00:11:05,166 --> 00:11:07,100 Ioannis examines the mud core close 146 00:11:07,100 --> 00:11:09,634 up at the University of Patras. 147 00:11:18,634 --> 00:11:21,266 NARRATOR: Ioannis scrutinizes the layer's contents. 148 00:11:37,467 --> 00:11:40,040 NARRATOR: His team searches for any tiny shells. 149 00:11:40,040 --> 00:11:41,000 NARRATOR: His team searches for any tiny shells. 150 00:11:41,000 --> 00:11:43,900 They might not be much larger than grains of sand. 151 00:11:50,467 --> 00:11:52,734 For precise identification, 152 00:11:52,734 --> 00:11:56,166 the team creates images using an electron microscope. 153 00:11:57,867 --> 00:12:00,867 These are creatures called ostracods, 154 00:12:00,867 --> 00:12:03,467 particular species that prefer to live in the mix 155 00:12:03,467 --> 00:12:06,634 of salt and fresh water found in a lagoon. 156 00:12:10,266 --> 00:12:14,734 The presence of these ostracod species confirms Dora's theory. 157 00:12:15,734 --> 00:12:18,967 Helike was covered by a lagoon, 158 00:12:19,000 --> 00:12:21,734 which then itself disappears 159 00:12:21,734 --> 00:12:24,533 thanks to this area's ever changing landscape. 160 00:12:29,734 --> 00:12:33,266 Local rivers erode nearby mountains. 161 00:12:34,100 --> 00:12:36,734 and fill with huge amounts of sediment. 162 00:12:40,367 --> 00:12:44,367 Over many years, the rivers dump this debris 163 00:12:44,367 --> 00:12:46,533 once they reach the coastal plain. 164 00:12:50,634 --> 00:12:53,634 The buildup of silt produces new banks 165 00:12:53,634 --> 00:12:57,634 and channels, drastically changing the local landscape. 166 00:12:59,800 --> 00:13:01,900 It's likely the lagoon above ancient 167 00:13:01,900 --> 00:13:05,367 Helike gradually fills up with river sediment. 168 00:13:05,367 --> 00:13:08,467 The sea lake turns into dry land 169 00:13:08,467 --> 00:13:10,040 and conceals Helike completely. 170 00:13:10,040 --> 00:13:10,734 and conceals Helike completely. 171 00:13:13,166 --> 00:13:15,533 Dora and the team's detective work 172 00:13:15,533 --> 00:13:19,467 finally solves a centuries-old mystery. 173 00:13:19,467 --> 00:13:21,433 They found Helike. 174 00:13:23,600 --> 00:13:25,100 For 20 years, 175 00:13:25,100 --> 00:13:26,900 the team digs deep trenches through 176 00:13:26,900 --> 00:13:30,467 the sediments of the flat coastal plain. 177 00:13:30,467 --> 00:13:33,333 They unearth several pockets of settlement that 178 00:13:33,367 --> 00:13:36,333 span more than 2,000 years of occupation. 179 00:13:40,000 --> 00:13:40,040 What can archaeology reveal about 180 00:13:40,040 --> 00:13:42,634 What can archaeology reveal about 181 00:13:42,634 --> 00:13:45,166 Helike's status in ancient Greece? 182 00:13:46,100 --> 00:13:50,533 And could this help pinpoint the source of the Atlantis myth? 183 00:14:02,867 --> 00:14:04,533 NARRATOR: Helike, Greece, 184 00:14:05,967 --> 00:14:08,066 a long lost ancient city, 185 00:14:09,500 --> 00:14:13,634 now rediscovered by Dora Katsonopoulou and her team. 186 00:14:25,367 --> 00:14:27,734 NARRATOR: Among the ruins of Helike, 187 00:14:27,734 --> 00:14:28,280 archaeologists unearth two identical coins. 188 00:14:28,280 --> 00:14:31,266 archaeologists unearth two identical coins. 189 00:14:33,367 --> 00:14:37,533 They feature important clues about the ancient lost city. 190 00:14:39,467 --> 00:14:42,800 On one face, a laurel wreath surrounds 191 00:14:42,900 --> 00:14:46,367 two dolphins swimming either side of a trident spear. 192 00:14:48,700 --> 00:14:51,367 on the other, the head of the god Poseidon, 193 00:14:53,266 --> 00:14:57,166 next to a single word in Greek, Helike. 194 00:14:58,734 --> 00:15:01,367 What can these coins and the god 195 00:15:01,367 --> 00:15:04,533 depicted on them reveal about the city? 196 00:15:31,266 --> 00:15:34,367 NARRATOR: The great poet Homer, four centuries before 197 00:15:34,367 --> 00:15:36,166 Helike's destruction, 198 00:15:36,166 --> 00:15:40,000 remarks on great sacrifices made in Poseidon's honor. 199 00:15:41,266 --> 00:15:43,800 The locals choose this particular god 200 00:15:43,900 --> 00:15:46,433 because Helike is a port city. 201 00:16:00,100 --> 00:16:03,066 NARRATOR: The citizens' fortunes depend on the sea 202 00:16:03,066 --> 00:16:06,800 and, they believe, on the moods of its chief deity. 203 00:16:09,166 --> 00:16:12,100 Poseidon is the brother of Zeus and Hades. 204 00:16:13,166 --> 00:16:16,634 He carries a three-pronged spear called a trident 205 00:16:16,634 --> 00:16:18,734 and is one of the most important gods 206 00:16:18,734 --> 00:16:20,166 in the Greek pantheon. 207 00:16:22,367 --> 00:16:26,367 Poseidon reigns over all rivers and seas, 208 00:16:26,433 --> 00:16:28,280 leaving Zeus to rule the heavens and Hades 209 00:16:28,280 --> 00:16:29,533 leaving Zeus to rule the heavens and Hades 210 00:16:29,533 --> 00:16:30,734 the underworld. 211 00:16:32,367 --> 00:16:36,800 His bad temper generates storms and floods. 212 00:16:36,900 --> 00:16:40,467 With a strike of his trident, he sets off earthquakes. 213 00:16:44,000 --> 00:16:47,467 Superstitious sailors make offerings of animals to 214 00:16:47,533 --> 00:16:51,433 appease Poseidon's wrath before setting out to sea. 215 00:16:54,634 --> 00:16:58,000 Dora investigates exactly how important the port 216 00:16:58,000 --> 00:16:58,280 of Helike is in the ancient world. 217 00:16:58,280 --> 00:17:00,634 of Helike is in the ancient world. 218 00:17:02,100 --> 00:17:05,266 In recent excavations, the team unearths over 219 00:17:05,266 --> 00:17:07,066 a hundred coins. 220 00:17:07,066 --> 00:17:09,900 Almost all of them are not minted in Helike. 221 00:17:22,700 --> 00:17:24,533 NARRATOR: Coins from visitors far 222 00:17:24,634 --> 00:17:28,100 and wide reveal Helike's widespread importance. 223 00:17:29,266 --> 00:17:31,166 It's the major stop off point for 224 00:17:31,233 --> 00:17:33,533 ships traveling along the Gulf of Corinth. 225 00:17:46,600 --> 00:17:50,266 NARRATOR: This traffic and trade allows Helike's stature to 226 00:17:50,333 --> 00:17:51,900 increase ever further. 227 00:17:59,100 --> 00:18:00,734 In its golden age, 228 00:18:00,800 --> 00:18:03,634 Helike leads an alliance of 12 city-states 229 00:18:03,634 --> 00:18:06,333 in the Achaea region of ancient Greece. 230 00:18:10,166 --> 00:18:12,066 The city plays a leading role in 231 00:18:12,100 --> 00:18:14,800 Homer's epic story of the siege of Troy. 232 00:18:18,634 --> 00:18:20,867 Helike's cultural influence 233 00:18:20,867 --> 00:18:24,000 spreads across the Mediterranean, 234 00:18:24,000 --> 00:18:27,233 as it establishes colonies in Italy and Asia Minor. 235 00:18:30,500 --> 00:18:34,367 Helike's sanctuary of Poseidon attracts pilgrims from far 236 00:18:34,367 --> 00:18:35,533 and wide, 237 00:18:35,533 --> 00:18:39,233 spreading the city's fame across the ancient world. 238 00:18:40,700 --> 00:18:42,367 However, 239 00:18:42,367 --> 00:18:45,233 Helike's high status is unstable. 240 00:18:47,367 --> 00:18:48,634 Ioannis Koukouvelas 241 00:18:48,634 --> 00:18:50,800 believes there's a second reason 242 00:18:50,900 --> 00:18:53,100 Helike's citizens choose to worship Poseidon. 243 00:18:56,100 --> 00:18:58,280 The bad-tempered god of the sea has another name, 244 00:18:58,280 --> 00:18:59,634 The bad-tempered god of the sea has another name, 245 00:18:59,634 --> 00:19:01,166 the earth shaker. 246 00:19:21,266 --> 00:19:23,166 NARRATOR: Helike prospers thanks 247 00:19:23,166 --> 00:19:26,166 to its links to Poseidon, the sea god, 248 00:19:26,166 --> 00:19:28,280 but as god of earthquakes, he brings destruction. 249 00:19:28,280 --> 00:19:29,734 but as god of earthquakes, he brings destruction. 250 00:19:31,600 --> 00:19:33,600 What sequence of events causes 251 00:19:33,600 --> 00:19:36,367 the thriving city to vanish overnight 252 00:19:36,367 --> 00:19:38,800 in 373 BCE, 253 00:19:39,500 --> 00:19:43,233 and is there any escape for Helike's residents? 254 00:19:58,367 --> 00:20:01,100 NARRATOR: The ancient city of Helike 255 00:20:01,100 --> 00:20:03,433 disappears in 373 BCE. 256 00:20:05,467 --> 00:20:07,734 in the hills above its buried ruins, 257 00:20:08,634 --> 00:20:11,000 Ioannis Koukouvelas searches for the cause 258 00:20:11,000 --> 00:20:12,800 of the city's disappearance. 259 00:20:16,867 --> 00:20:19,120 The exposed rock reveals clues 260 00:20:19,120 --> 00:20:19,333 The exposed rock reveals clues 261 00:20:19,367 --> 00:20:21,800 to the area's recent geological past. 262 00:20:22,634 --> 00:20:25,867 There are several steps called offsets 263 00:20:25,867 --> 00:20:29,433 where layers of sediment suddenly drop downwards. 264 00:20:59,166 --> 00:21:01,867 NARRATOR: The offsets reveal this coast is prone 265 00:21:01,900 --> 00:21:04,433 to one of nature's most destructive forces, 266 00:21:04,500 --> 00:21:05,967 earthquakes. 267 00:21:13,900 --> 00:21:16,867 NARRATOR: The larger the offset, the greater the tremor that 268 00:21:16,867 --> 00:21:17,967 causes it. 269 00:21:31,900 --> 00:21:34,367 NARRATOR: One of these large offsets matches 270 00:21:34,367 --> 00:21:37,967 the strong earthquake that spells disaster for Helike. 271 00:21:40,734 --> 00:21:44,634 On a winter's night of 373 BCE, 272 00:21:44,634 --> 00:21:46,634 an earthquake of a magnitude above 273 00:21:46,634 --> 00:21:49,120 6 on the Richter scale strikes Helike. 274 00:21:49,120 --> 00:21:49,867 6 on the Richter scale strikes Helike. 275 00:21:51,367 --> 00:21:53,634 According to ancient eyewitnesses, 276 00:21:53,734 --> 00:21:56,533 immense columns of flames erupt from cracks in 277 00:21:56,533 --> 00:22:01,066 the ground -- their light shines across the city. 278 00:22:02,600 --> 00:22:07,367 Tremors rock the buildings, reducing them to rubble. 279 00:22:07,367 --> 00:22:11,800 Then, astonishingly, the whole of Helike sinks into the ground. 280 00:22:14,600 --> 00:22:16,467 Can this terrifying tale of 281 00:22:16,467 --> 00:22:19,120 the earth engulfing entire buildings be true? 282 00:22:19,120 --> 00:22:19,900 the earth engulfing entire buildings be true? 283 00:22:24,000 --> 00:22:27,166 Christian Malaga Chuquitaype of Imperial College 284 00:22:27,233 --> 00:22:29,066 London investigates. 285 00:22:29,867 --> 00:22:31,967 Is it possible for full buildings 286 00:22:32,000 --> 00:22:34,734 or structures to be swallowed by the earth? 287 00:22:34,800 --> 00:22:36,900 So what I'm going to do here is offer you 288 00:22:36,900 --> 00:22:39,333 a demonstration of what happens when an earthquake hits 289 00:22:39,367 --> 00:22:40,967 saturated soil. 290 00:22:41,000 --> 00:22:44,533 NARRATOR: This high-tech shaking table replicates what happens 291 00:22:44,533 --> 00:22:48,433 when an earthquake strikes -- like many coastal cities, 292 00:22:48,500 --> 00:22:49,120 Helike is built on sandy soil just above the water level. 293 00:22:49,120 --> 00:22:52,634 Helike is built on sandy soil just above the water level. 294 00:22:53,467 --> 00:22:56,867 I'm just, um, mixing, 295 00:22:56,867 --> 00:22:59,367 allowing the water to go deeper. 296 00:22:59,367 --> 00:23:01,634 NARRATOR: Christian places model structures into 297 00:23:01,734 --> 00:23:05,734 the tank, which contains sand saturated with water. 298 00:23:06,734 --> 00:23:09,367 CHRISTIAN: The soil at this stage, although it has water, 299 00:23:09,367 --> 00:23:12,433 it's able to sustain the weight of the structure 300 00:23:12,500 --> 00:23:13,900 and keep it in place. 301 00:23:15,100 --> 00:23:17,867 NARRATOR: Ancient Helike's buildings are well supported, 302 00:23:17,867 --> 00:23:19,120 but the saturated ground is vulnerable to seismic activity. 303 00:23:19,120 --> 00:23:22,333 but the saturated ground is vulnerable to seismic activity. 304 00:23:24,000 --> 00:23:26,533 Christian's table replicates an earthquake's 305 00:23:26,533 --> 00:23:28,634 rapid back and forth shaking. 306 00:23:30,533 --> 00:23:31,967 So it's going now. 307 00:23:33,867 --> 00:23:36,433 [rapid shaking noises] 308 00:23:36,500 --> 00:23:39,066 NARRATOR: The earthquake first knocks buildings over. 309 00:23:40,467 --> 00:23:43,066 Then they start to sink into the ground. 310 00:23:44,634 --> 00:23:47,900 What happens is that the water pressure inside 311 00:23:47,900 --> 00:23:49,120 the sand starts to increase, and at some point, 312 00:23:49,120 --> 00:23:50,634 the sand starts to increase, and at some point, 313 00:23:50,634 --> 00:23:54,367 it breaks all the capacity that the sand has to sustain 314 00:23:54,367 --> 00:23:57,967 the structures on top of it -- the sand is 315 00:23:58,000 --> 00:24:01,867 unable to sustain the load of the buildings. 316 00:24:01,867 --> 00:24:05,233 NARRATOR: This phenomenon is called soil liquefaction. 317 00:24:06,166 --> 00:24:08,100 The tremors cause underground water 318 00:24:08,100 --> 00:24:10,533 to overcome the sand's supportive power. 319 00:24:13,533 --> 00:24:16,634 The science shows model buildings will partially, 320 00:24:16,634 --> 00:24:19,120 but not completely, disappear into once solid ground. 321 00:24:19,120 --> 00:24:20,233 but not completely, disappear into once solid ground. 322 00:24:25,600 --> 00:24:30,467 Five days before the disaster, animals flee the city, 323 00:24:30,467 --> 00:24:33,734 perhaps sensing tremors in the ground beneath their feet. 324 00:24:35,700 --> 00:24:38,734 On the fateful night the earthquake rocks Helike, 325 00:24:39,533 --> 00:24:42,967 soil liquefaction sucks buildings into the ground. 326 00:24:43,900 --> 00:24:46,734 Few citizens can flee the annihilation. 327 00:24:48,467 --> 00:24:49,120 Ten Spartan ships anchored in Helike's harbor 328 00:24:49,120 --> 00:24:51,634 Ten Spartan ships anchored in Helike's harbor 329 00:24:51,634 --> 00:24:54,333 are dragged down into the ocean. 330 00:24:58,867 --> 00:25:01,734 A 2,000-strong rescue team from neighboring 331 00:25:01,800 --> 00:25:05,634 cities searches for survivors, to no avail. 332 00:25:09,467 --> 00:25:12,066 Christian's first demonstration shows 333 00:25:12,100 --> 00:25:15,333 buildings can be partially swallowed by sandy soil. 334 00:25:17,100 --> 00:25:19,120 But to test whether liquefaction can consume 335 00:25:19,120 --> 00:25:19,533 But to test whether liquefaction can consume 336 00:25:19,533 --> 00:25:23,100 the entire city, as ancient sources claim, 337 00:25:23,100 --> 00:25:24,634 he sets the shaking table to 338 00:25:24,634 --> 00:25:27,900 the equivalent of 8 on the Richter scale. 339 00:25:27,900 --> 00:25:30,467 This matches some of the strongest earthquakes 340 00:25:30,467 --> 00:25:31,533 ever recorded. 341 00:25:31,600 --> 00:25:33,634 I'll start. Yep. 342 00:25:36,266 --> 00:25:38,967 [loud rattling noises] 343 00:25:43,634 --> 00:25:46,433 NARRATOR: The buildings begin to sink. 344 00:25:46,500 --> 00:25:49,120 But as they do, the sand beneath compresses. 345 00:25:49,120 --> 00:25:49,800 But as they do, the sand beneath compresses. 346 00:25:50,634 --> 00:25:53,266 Eventually, the ground firms up 347 00:25:53,266 --> 00:25:55,533 enough to bear the structure's weight. 348 00:25:56,700 --> 00:26:00,867 You can see that the building here, it's not fully sinked. 349 00:26:00,900 --> 00:26:03,367 Even if you have a very, very strong shaking, 350 00:26:03,367 --> 00:26:07,266 I would expect buildings to tilt, buildings to break, 351 00:26:07,266 --> 00:26:10,967 and some parts of them to be swallowed, 352 00:26:12,100 --> 00:26:15,533 but the idea of whole buildings 353 00:26:15,533 --> 00:26:19,000 just completely disappearing into the ground 354 00:26:19,000 --> 00:26:19,120 is probably a bit of a literary freedom. 355 00:26:19,120 --> 00:26:23,734 is probably a bit of a literary freedom. 356 00:26:25,166 --> 00:26:27,166 NARRATOR: Liquefaction very likely 357 00:26:27,233 --> 00:26:29,900 plays a part in Helike's fate. 358 00:26:29,900 --> 00:26:33,000 But liquefaction alone can't cause an entire city 359 00:26:33,000 --> 00:26:34,066 to disappear. 360 00:26:36,266 --> 00:26:39,433 What really wipes out Helike? 361 00:26:39,500 --> 00:26:41,166 Will evidence on the ground 362 00:26:41,166 --> 00:26:44,066 match the extraordinary ancient accounts? 363 00:26:56,734 --> 00:26:58,900 NARRATOR: In 373 BCE, Helike, 364 00:27:00,367 --> 00:27:04,100 one of the great cities of ancient Greece, disappears. 365 00:27:05,500 --> 00:27:07,367 A team of scientists seek to 366 00:27:07,367 --> 00:27:10,233 piece together its fatal final days. 367 00:27:13,867 --> 00:27:15,533 After the earthquake, 368 00:27:15,533 --> 00:27:19,066 ancient texts report a rapidly rising sea. 369 00:27:20,166 --> 00:27:21,200 Then they state water completely submerges the city. 370 00:27:21,200 --> 00:27:23,900 Then they state water completely submerges the city. 371 00:27:27,100 --> 00:27:28,367 Ioannis Koukouvelas 372 00:27:28,433 --> 00:27:31,800 suspects the accounts describe another natural phenomenon. 373 00:27:59,266 --> 00:28:02,900 NARRATOR: When Dora's team examines Helike's buried ruins, 374 00:28:03,000 --> 00:28:06,066 they spot something unusual about the settlement. 375 00:28:07,266 --> 00:28:10,533 A set of stones lies scattered at ground level. 376 00:28:13,266 --> 00:28:16,533 The stones once formed the lower section of a wall of 377 00:28:16,634 --> 00:28:21,200 a house -- a powerful blow has pushed it over. 378 00:28:21,200 --> 00:28:21,333 a house -- a powerful blow has pushed it over. 379 00:28:25,266 --> 00:28:27,900 This could come from a natural phenomenon. 380 00:28:31,266 --> 00:28:33,900 Could this be evidence that a tsunami 381 00:28:34,000 --> 00:28:37,734 provides the knockout blow that seals Helike's fate? 382 00:28:48,266 --> 00:28:51,200 Ioannis Karmpadakis models Earth's biggest waves 383 00:28:51,200 --> 00:28:52,467 Ioannis Karmpadakis models Earth's biggest waves 384 00:28:52,533 --> 00:28:56,333 in these 75-foot-long tanks at Imperial College, London. 385 00:29:10,867 --> 00:29:12,900 Ioannis wants to find out whether 386 00:29:13,000 --> 00:29:16,333 a tsunami could cause Helike's pattern of destruction. 387 00:29:18,600 --> 00:29:21,200 A tsunami starts when an underwater earthquake 388 00:29:21,200 --> 00:29:21,500 A tsunami starts when an underwater earthquake 389 00:29:21,500 --> 00:29:24,900 or landslide stirs a large volume of water. 390 00:29:34,967 --> 00:29:37,367 NARRATOR: In deep water, the wave is small. 391 00:29:38,266 --> 00:29:42,467 But as the tsunami squeezes into the shallows, it changes. 392 00:29:58,000 --> 00:30:02,266 NARRATOR: The initial tsunami isn't enough to push down walls. 393 00:30:02,266 --> 00:30:04,734 There is a secondary phenomenon at play. 394 00:30:05,967 --> 00:30:08,634 Ioannis adds loose material to represent 395 00:30:08,734 --> 00:30:10,900 debris created by the earthquake. 396 00:30:14,734 --> 00:30:17,533 The incoming wave uproots this debris. 397 00:30:31,266 --> 00:30:34,533 NARRATOR: The wave retreats, but it's now loaded with 398 00:30:34,634 --> 00:30:38,433 debris, ready to smash anything in its way. 399 00:30:49,634 --> 00:30:51,200 NARRATOR: The experiment explains why the destroyed 400 00:30:51,200 --> 00:30:52,266 NARRATOR: The experiment explains why the destroyed 401 00:30:52,333 --> 00:30:56,734 wall falls towards rather than away from the incoming sea 402 00:30:58,066 --> 00:31:02,533 and proves it is very possible a tsunami strikes Helike. 403 00:31:06,734 --> 00:31:09,634 Now, Ioannis investigates if a tsunami can 404 00:31:09,634 --> 00:31:12,266 be big enough to engulf the entire city, 405 00:31:12,266 --> 00:31:14,634 as the ancient texts describe. 406 00:31:16,500 --> 00:31:19,967 The geological evidence suggests Helike's earthquake 407 00:31:19,967 --> 00:31:21,200 peaks at around 6.5 on the Richter scale. 408 00:31:21,200 --> 00:31:23,467 peaks at around 6.5 on the Richter scale. 409 00:31:29,367 --> 00:31:31,266 NARRATOR: The waves in the previous experiment 410 00:31:31,266 --> 00:31:33,166 match massive earthquakes, 411 00:31:33,166 --> 00:31:35,900 around magnitude 8 on the Richter scale. 412 00:31:46,000 --> 00:31:49,266 NARRATOR: A smaller earthquake reduces the height of the wave 413 00:31:49,266 --> 00:31:51,200 and therefore the distance the water can reach inland. 414 00:31:51,200 --> 00:31:52,333 and therefore the distance the water can reach inland. 415 00:31:54,266 --> 00:31:56,266 Enough to damage some buildings 416 00:31:56,266 --> 00:31:58,600 but not to swamp the entire city, 417 00:31:58,600 --> 00:32:00,900 as the ancient texts describe. 418 00:32:22,600 --> 00:32:25,600 NARRATOR: Rather than a single devastating wave, 419 00:32:25,600 --> 00:32:27,634 the evidence shows the ancient accounts 420 00:32:27,734 --> 00:32:31,800 miss or misinterpret a more complex chain of events. 421 00:32:38,967 --> 00:32:42,266 The earthquake creates a 6-foot-high tsunami 422 00:32:42,266 --> 00:32:45,066 that wipes out the boats in Helike's Harbor. 423 00:32:47,500 --> 00:32:50,333 As the destructive wave washes inland, 424 00:32:51,500 --> 00:32:54,233 it destroys the walls of some buildings. 425 00:32:57,967 --> 00:32:59,867 The tremors also break a natural 426 00:32:59,867 --> 00:33:02,800 river dam in the mountains behind Helike, 427 00:33:02,900 --> 00:33:05,600 releasing millions of gallons of fresh water 428 00:33:05,600 --> 00:33:07,333 onto sections of the city. 429 00:33:09,166 --> 00:33:13,266 Part of Helike's coastal plain drops several feet. 430 00:33:13,266 --> 00:33:15,734 This allows seawater to submerge all 431 00:33:15,800 --> 00:33:17,900 but the tallest buildings and trees. 432 00:33:20,000 --> 00:33:21,200 Dora Katsonopoulou's team 433 00:33:21,200 --> 00:33:22,000 Dora Katsonopoulou's team 434 00:33:22,000 --> 00:33:25,367 believe the influx of fresh and saltwater creates 435 00:33:25,367 --> 00:33:29,166 the lagoon that smothers most of Helike, until it too 436 00:33:29,166 --> 00:33:30,900 eventually disappears. 437 00:33:32,634 --> 00:33:34,367 At her latest dig site, 438 00:33:34,367 --> 00:33:37,900 she hunts for clues to how much of Helike survives. 439 00:33:43,166 --> 00:33:45,533 Okay. Good. 440 00:33:58,266 --> 00:34:01,066 NARRATOR: These ruins lie just a third of a mile 441 00:34:01,100 --> 00:34:03,367 from flooded parts of the ancient city. 442 00:34:04,467 --> 00:34:07,266 They date to a period of reconstruction after 443 00:34:07,266 --> 00:34:08,467 the earthquake. 444 00:34:31,634 --> 00:34:34,800 NARRATOR: Ancient workers dye cloth in these basins. 445 00:34:44,000 --> 00:34:46,734 NARRATOR: This site reveals not all of Helike 446 00:34:46,734 --> 00:34:49,734 and its people are overwhelmed by the disaster. 447 00:35:12,066 --> 00:35:15,166 NARRATOR: The lagoon drowns the earthquake-damaged remains 448 00:35:15,166 --> 00:35:19,333 of Helike's Poseidon statue temple and sacred sanctuary. 449 00:35:20,600 --> 00:35:21,200 But other parts escape. 450 00:35:21,200 --> 00:35:22,266 But other parts escape. 451 00:35:35,000 --> 00:35:36,166 NARRATOR: The mystery of 452 00:35:36,166 --> 00:35:38,533 Helike's fatal moment is solved. 453 00:35:43,166 --> 00:35:46,166 Ancient writers exaggerate a moderate earthquake that 454 00:35:46,233 --> 00:35:48,467 drags Helike's most famous monuments 455 00:35:48,467 --> 00:35:51,200 into the depths of a lagoon, 456 00:35:51,200 --> 00:35:51,367 into the depths of a lagoon, 457 00:35:51,433 --> 00:35:56,367 where they remained to astound fishermen for 500 years. 458 00:35:56,367 --> 00:35:58,266 On the outskirts of Helike, 459 00:35:58,266 --> 00:36:01,467 life resumes soon after the disaster. 460 00:36:02,500 --> 00:36:05,867 One final question remains. 461 00:36:05,867 --> 00:36:08,600 Why does this lost city's fate so 462 00:36:08,600 --> 00:36:12,734 closely mirror the legendary tale of Atlantis? 463 00:36:12,734 --> 00:36:16,166 Could the life story of Atlantis's creator provide 464 00:36:16,166 --> 00:36:17,533 some clues? 465 00:36:29,000 --> 00:36:33,634 NARRATOR: In 373 BCE, an earthquake triggers a cascade 466 00:36:33,734 --> 00:36:38,066 of events that submerge the ancient city of Helike. 467 00:36:42,266 --> 00:36:45,266 The city's tragic end echoes the story of 468 00:36:45,266 --> 00:36:48,634 the most famous lost kingdom of all, Atlantis. 469 00:36:50,900 --> 00:36:52,967 JASMINE: The story of Atlantis is something we all heard 470 00:36:53,000 --> 00:36:54,360 as children -- it's this story that captivates us, 471 00:36:54,360 --> 00:36:55,800 as children -- it's this story that captivates us, 472 00:36:55,800 --> 00:36:57,967 because not only is it a lost civilization 473 00:36:58,000 --> 00:36:59,266 that we want to uncover, 474 00:36:59,266 --> 00:37:01,634 but it's also a civilization that's submerged, 475 00:37:01,634 --> 00:37:03,967 destroyed by tsunami and earthquake. 476 00:37:05,100 --> 00:37:08,367 NARRATOR: Jasmine Elmer researches real life origins 477 00:37:08,367 --> 00:37:10,734 of ancient myths. 478 00:37:10,800 --> 00:37:13,100 She investigates whether Helike could be 479 00:37:13,100 --> 00:37:16,166 the inspiration for the great lost city of legend. 480 00:37:22,900 --> 00:37:24,360 Her research starts with ancient texts. 481 00:37:24,360 --> 00:37:25,967 Her research starts with ancient texts. 482 00:37:28,000 --> 00:37:31,734 Around 360 BCE, Greek philosopher Plato 483 00:37:31,800 --> 00:37:34,900 describes the lost land in two works -- 484 00:37:34,900 --> 00:37:36,734 the Timaeus and the Critias. 485 00:37:41,100 --> 00:37:43,066 So this is where we first see 486 00:37:43,100 --> 00:37:46,467 the actual words in the Greek, [speaking Greek], 487 00:37:46,467 --> 00:37:49,000 which means the island of Atlantis. 488 00:37:49,000 --> 00:37:52,533 It's the first time that Plato actually mentions Atlantis. 489 00:37:52,533 --> 00:37:54,360 NARRATOR: Plato's Atlantis story is an allegory, 490 00:37:54,360 --> 00:37:55,734 NARRATOR: Plato's Atlantis story is an allegory, 491 00:37:55,800 --> 00:38:00,066 a fable he concocts to teach a moral lesson. 492 00:38:00,066 --> 00:38:03,467 However, actual locations and events may allow 493 00:38:03,467 --> 00:38:06,533 him to inject some realism to the tale. 494 00:38:06,634 --> 00:38:09,734 I think it's a really good exploration to consider all 495 00:38:09,734 --> 00:38:11,100 those different points of view and the -- 496 00:38:11,100 --> 00:38:12,867 and the contemporary historical events that are 497 00:38:12,900 --> 00:38:17,166 going on to see if there is an inspiration there for Plato. 498 00:38:17,166 --> 00:38:20,900 NARRATOR: The first clue Helike could inspire Atlantis is that 499 00:38:20,900 --> 00:38:24,360 citizens of both places are devoted to the same god. 500 00:38:24,360 --> 00:38:25,166 citizens of both places are devoted to the same god. 501 00:38:25,166 --> 00:38:27,533 JASMINE: And in the center of the island is the temple 502 00:38:27,533 --> 00:38:28,734 to Poseidon. 503 00:38:28,734 --> 00:38:30,533 And the cult of Poseidon is obviously 504 00:38:30,533 --> 00:38:33,533 a really important part of Atlantean culture. 505 00:38:33,634 --> 00:38:36,100 And that's really similar in some ways to Helike, because 506 00:38:36,100 --> 00:38:37,333 the cult of Poseidon there 507 00:38:37,367 --> 00:38:40,333 was dominant and well known across the Greek world. 508 00:38:41,367 --> 00:38:44,233 NARRATOR: Plato writes the gods destroy Atlantis as 509 00:38:44,266 --> 00:38:47,166 a punishment for the arrogance of its citizens. 510 00:38:49,367 --> 00:38:54,333 This tale of retribution echoes a story told about Helike. 511 00:39:00,100 --> 00:39:04,100 Some citizens from Helike's colony in Asia Minor traveled 512 00:39:04,100 --> 00:39:07,233 back to their homeland on the advice of an oracle. 513 00:39:10,734 --> 00:39:13,266 They make a sacrifice to Poseidon 514 00:39:13,266 --> 00:39:15,266 and reveal a plan to take back 515 00:39:15,266 --> 00:39:18,333 sacred relics that belong to their forefathers. 516 00:39:22,367 --> 00:39:24,166 The inhabitants of Helike are 517 00:39:24,166 --> 00:39:24,360 affronted and murder their visitors. 518 00:39:24,360 --> 00:39:26,967 affronted and murder their visitors. 519 00:39:30,900 --> 00:39:33,734 Poseidon is angered by this outrage. 520 00:39:33,800 --> 00:39:37,467 He punishes Helike and its impious citizens with 521 00:39:37,467 --> 00:39:40,066 a cataclysmic earthquake and tsunami. 522 00:39:44,533 --> 00:39:48,533 The connections between Helike and Atlantis are clear. 523 00:39:48,634 --> 00:39:50,634 Both worship Poseidon. 524 00:39:50,634 --> 00:39:53,433 Both are destroyed and then disappear. 525 00:39:57,000 --> 00:39:59,467 There was an earthquake, there was a tsunami, 526 00:39:59,467 --> 00:40:02,266 there was a flood, and also there is this sort of odd 527 00:40:02,266 --> 00:40:04,967 description of sinking into the earth 528 00:40:05,900 --> 00:40:07,367 in the same way that you get a kind of 529 00:40:07,367 --> 00:40:10,900 liquefaction that's going on as part of the Helike disaster. 530 00:40:12,166 --> 00:40:14,800 NARRATOR: The final clue that Plato has Helike in 531 00:40:14,800 --> 00:40:18,433 mind is when he writes the legend of Atlantis. 532 00:40:19,700 --> 00:40:21,734 Helike is the disaster that happens only 533 00:40:21,734 --> 00:40:24,333 about 15 years before he writes his dialogues. 534 00:40:24,367 --> 00:40:26,734 So it kind of makes sense that this is an event, 535 00:40:26,734 --> 00:40:28,266 a contemporary event that is happening, 536 00:40:28,266 --> 00:40:30,533 it would have been a very well known disaster. 537 00:40:30,533 --> 00:40:33,867 It makes sense that Plato would perhaps have knowledge of that. 538 00:40:35,867 --> 00:40:37,867 NARRATOR: Jasmine believes it's possible 539 00:40:37,900 --> 00:40:40,533 Plato recycles what he hears of Helike 540 00:40:40,533 --> 00:40:43,634 to bring to life his own disaster story. 541 00:40:44,600 --> 00:40:46,800 In the long search for Atlantis, 542 00:40:46,800 --> 00:40:50,967 the trail strongly leads towards one real life lost city. 543 00:40:53,100 --> 00:40:54,360 After a decades-long quest, 544 00:40:54,360 --> 00:40:55,433 After a decades-long quest, 545 00:40:55,500 --> 00:40:58,066 the story of Helike can finally be written. 546 00:40:59,734 --> 00:41:02,266 One of the great ports of ancient Greece, 547 00:41:02,266 --> 00:41:06,266 it rises, thanks to its Poseidon cult, to dominate 548 00:41:06,266 --> 00:41:07,734 the Gulf of Corinth. 549 00:41:08,800 --> 00:41:12,967 The city falls in the earthquake of 373 BCE. 550 00:41:14,467 --> 00:41:17,533 Its sanctuary and statue disappear underwater for 551 00:41:17,533 --> 00:41:19,266 five centuries, 552 00:41:19,266 --> 00:41:23,333 then vanish completely for almost two millennia 553 00:41:25,700 --> 00:41:28,634 until Helike's rediscovery today.