Classification: Unverified account

Cuba’s “sunken city”: what sonar found off Guanahacabibes

A shipwreck survey revealed geometric shapes as deep as 750 metres. Sonar, a small underwater robot and an unsampled plate fed the lost-city theory, but the evidence does not yet establish a city.

Península de Guanahacabibes, Pinar del Río, Cuba · See stories from this place and nearby

The expedition was not looking for Atlantis

In 2000, a Cuban-Canadian expedition surveyed the seabed near the Guanahacabibes Peninsula at Cuba’s western tip. Exploramar was primarily looking for shipwrecks. Near the foot of Bajo de San Antonio, hundreds of metres below the surface, side-scan sonar picked up a group of unusual shapes. The team called the area MEGA. Cuban geologist Manuel A. Iturralde-Vinent, who took part in the investigation, placed the features roughly 600 to 750 metres deep offshore from the peninsula. Nocturna’s map marker denotes only the approximate region, not a verified coordinate for each feature.

Sonar is not a camera. It sends out acoustic waves and turns reflected signals from the seabed into a contrast map. Some larger shapes seemed to line up at angles. Engineer Paulina Zelitsky interpreted sections as corridors, rooms and heavy walls. A suggestive image, however, cannot tell us whether a line was carved, built, moved by a landslide or emphasised by image processing. The headline about a “sunken city” grew in the gap between observation and interpretation.

What the robot actually saw

After mapping, the team lowered a small remotely operated vehicle named Rob to take photographs and video near the bottom. It did not reveal streets and building fronts. It recorded scattered rock blocks, some irregular and others polyhedral. Iturralde described one roughly square block and another, about a metre across, with a pyramidal shape. His report distinguishes the large sonar features, tens or even a hundred metres long, from smaller blocks seen up close. This matters: a sonar trace that resembles a “wall” is not a wall excavated and measured by archaeologists.

One detail rarely survives the viral retellings. Iturralde saw erosion marks on some surfaces consistent with the action of currents. The team collected bottom sediments and small fragments from the area, including material resembling volcanic scoria and pebbles. Those samples are not identified pieces of the geometric blocks themselves; the geologist said the composition of those blocks remained unknown. Finding fragments in a seabed sample therefore proves neither a constructed city nor the provenance of the larger stones.

Another image especially puzzled him: a grey plate about 20 to 30 centimetres long, embedded in rock near 700 metres depth. From a distance, he thought it might be metallic. The vehicle did not retrieve a sample. Without a material analysis, a date or a provenance, “metal” remains a visual impression, not a laboratory identification. The team attempted to return, but, in Iturralde’s later account, the vehicle’s cable lost communication at around 500 metres. The question stayed beyond the expedition’s reach.

How a possibility became a city in headlines

The story spread internationally in 2001. Sonar images and descriptions of geometric stones travelled alongside claims about an ancient city, an unknown civilisation and even Atlantis. Yet in December of that year Zelitsky told the press it was too early to decide whether the structures were human-built or natural. Journalists interviewed the team and outside specialists in 2002; their question-mark headlines reflected an open inquiry, not a completed archaeological discovery.

Images of intact pyramids and underwater avenues now attached to many retellings are not photographs of the site. Iturralde explained in 2024 that most of the larger features lie under sand and that the spectacular views are artistic reconstructions. Readers can compare the actual sonar figures and photographs of blocks in his report. Their restraint is precisely what makes them useful: they show less, and require more care, than online illustrations.

The 600-metre problem

A common suggestion is that rising seas at the end of the last ice age covered the city. The scale does not work on its own. The IPCC estimates that global mean sea level at the Last Glacial Maximum was about 125 to 134 metres below today’s level. MEGA’s features are 600 to 750 metres deep. Ordinary postglacial sea-level rise alone therefore cannot turn that seabed into recently habitable dry land. A much greater vertical displacement of the ground would also need to be demonstrated, with a plausible geological mechanism and date.

Iturralde noted slope breaks and nearby signs of submarine landslides, but warned that available data cannot establish whether the MEGA area was ever above water. Depth also cannot date a supposed city by simple arithmetic. Until human occupation and the site’s geological history are established, ages assigned to the “ruins” remain speculative.

Three explanations, no verdict

In a preliminary report presented in 2014, Iturralde considered three possibilities: entirely natural features; human constructions; or natural formations later modified by people. Faults and fractures, karst dissolution, currents, erosion and mass movement can produce striking geometry. At the same time, some repeated alignments and the appearance of particular blocks warrant careful inspection. None of these observations alone separates construction from geological coincidence.

According to the geologist, disagreements among participants brought the investigation to a halt in 2005. In a 2024 interview he said there had been no new fieldwork at the site since then and that another mission would require substantial funding. His 2014 report is a preliminary examination of expedition data, not a conclusive excavation or an independent archaeological date.

A useful next mission would repeat the survey with modern sonar, publish georeferenced maps, obtain continuous images of the larger formations, sample the blocks and plate directly, analyse the rock types and search for artefacts in a verifiable stratigraphic context. Only then would it make sense to investigate an age and any connection to human activity.

Where the evidence ends

The find is real: acoustic records of unusual shapes and images of rocks in deep water. There is no published demonstration of streets, buildings, dated artefacts or a city built by humans. This case remains compelling because it shows how a technical image, a halted expedition and later illustrations can merge into an apparent certainty. Off Guanahacabibes, the honest question remains open: what processes made those shapes?

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