Nestled some 650 metres (2,000 feet) beneath the waves surrounding Cuba lies one of archaeology’s great unsolved mysteries.

In 2000, researchers from the Canadian company Advanced Digital Communications (ADC) were surveying the waters off the tip of the Guanahacabibes Peninsula, when their sonar equipment picked up a strange series of structures down on the ocean floor.

The images generated by the scanning equipment showed smooth symmetrically organised stones reminiscent of an urban development, BBC News reported at the time.

In July 2001, the ADC team – led by marine engineer Pauline Zelitsky and her husband Paul Weinzweig – returned to the site, this time with an explorative robot device capable of conducting advanced underwater filming.

The images captured by this robot confirmed the presence of smooth blocks with the appearance of cut granite – some of which measured eight by 10 feet (2.43 by three metres) – as well as other geometric shapes.

Some of the stones appeared deliberately stacked on top of one another like pyramids, while others were circular.

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