This episode explores whether submerged structures around the world might preserve evidence of advanced ancient civilizations—or even extraterrestrial contact. Ancient astronaut theorists point to sites like the stepped stone formation off Japan's coast, which some claim could predate the Egyptian pyramids, and recently discovered temple ruins beneath Peru's Lake Titicaca, which local legends associate with an underwater UFO base. Giorgio Tsoukalos and David Childress argue that more than 200 sunken cities in the Mediterranean alone suggest sophisticated urban centers existed when mainstream archaeology says no such cities should exist. The episode presents Plato's account of Atlantis as potentially describing an alien metropolis founded by the god Poseidon, interpreted here as an extraterrestrial being, while ancient Indian Sangam texts are cited as describing sunken cities where humans and aliens once intermingled.
Mainstream science offers a straightforward explanation: during the last Ice Age, sea levels were up to 400 feet lower than today, and as massive ice sheets melted between 21,000 and 10,000 years ago, roughly ten million square miles of inhabited coastal land flooded worldwide. Graham Hancock's observation that this area—equivalent to Europe and China combined—remains largely unexplored underwater is actually common ground between conventional archaeology and alternative theorists. The episode succeeds in highlighting a genuine mystery: we've barely begun systematically surveying these submerged landscapes, meaning significant archaeological discoveries likely still await in waters that once were thriving shorelines.
Chaco Canyon
United States · Ancestral Puebloan
Great Houses aligned precisely to solar and lunar cycles — impossible without alien knowledge
Gulf of Khambhat (Gulf of Cambay) Underwater Ruins
India · Ancient Indian / Indus Valley
Theorists argue the enormous network of stone buildings covering five square miles on the floor of the Gulf of Khambhat represents a lost city predating all known civilizations, with artifacts dated as far back as 32,000 years, supporting Hindu scholarly claims that Indian civilization extends tens of thousands of years into the past. Mainstream oceanographers concluded the area was submerged approximately 9,000 years ago, and the Indian government-commissioned survey that discovered the site was originally intended to study pollution.
Kumari Kandam (submerged landmass south of India)
India · Ancient Indian / Indus Valley
Theorists argue that Kumari Kandam, described in Tamil Sangam literature as a now-submerged landmass where the first two Sangam assemblies of sages took place, was a real inhabited land that also hosted extraterrestrial beings, corroborating the underwater discoveries in the Gulf of Khambhat and off Dwaraka. The Sangam texts are ancient Tamil literary works whose geographic references to a sunken southern landmass are debated by scholars as mythological or as possible cultural memory of post-Ice Age sea level rise.
Lake Titicaca
Peru / Bolivia · Tiwanaku / Inca
Submerged temple ruins discovered beneath the lake
Lake Titicaca Temple Ruins
Peru · Andean
Ancient Aliens suggests underwater temple ruins beneath Lake Titicaca support local legends of an underwater UFO base where aliens and humans intermingled. The show proposes these structures as evidence of extraterrestrial visitation.
Nan Madol
Micronesia · Saudeleur
Venice of the Pacific — built on artificial islands using massive basalt columns
Sahara Desert Cave Paintings
Algeria/Libya · Cro-Magnon / Upper Paleolithic
Ancient astronaut theorists argue that cave paintings from the Sahara Desert depict beings wearing astronaut suits, and that these images form a global pattern of extraterrestrial contact alongside Japan's Dogu figures and the Hopi kachina dolls of North America. Mainstream archaeology interprets the Saharan cave paintings, such as those at Tassili n'Ajjer, as ritual or ceremonial art depicting humans and animals from prehistoric North African cultures.
Underwater Ruins off Western Cuba
Cuba · Hypothetical Extraterrestrial
Theorists argue the symmetrical stone structures found over half a mile below the seafloor off western Cuba represent the remains of a prehistoric city possibly connected to Atlantis, citing 30 geometric structures including apparent streets, buildings, tunnels, and pyramids. Geologists using volcanic ash dating estimated the site sank over 6,000 years ago, though mainstream archaeology has not confirmed a human-built origin.
Utsuro Bune Landing Site (beach north of Tokyo)
Japan · Japanese
Ancient astronaut theorists argue that the 1803 legend of the Utsuro Bune — a large round hollow craft that washed ashore on a beach north of Tokyo carrying an unknown woman with unidentifiable writing and a mysterious box — describes a genuine extraterrestrial craft, supported by five nearly identical drawings from different regions of Japan resembling modern UFO reports. Mainstream historians treat the Utsuro Bune as a folkloric legend of uncertain origin, with no physical evidence to support a literal interpretation.
Yonaguni Monument
Japan · Unknown / Possible Natural
An underwater stone structure off Yonaguni Island appears to be a man-made pyramid and terrace complex