A series of strange geometric structures on the ocean floor have left boffins baffled. The structures, which are thought to be older than the Egyptian pyramids, are gaining more attention despite being found around 20 years ago.
Located off the coast of Cuba, a worker found a series of perfectly aligned geometric shapes, arranged at sharp right angles. Originally, the crew were running a routine ocean-mapping mission, but their sonar technology picked up on something completely unexpected back in the early 2000s.
The firm, Advanced Digital Communications, found images of massive, smooth blocks lying on the seabed. They appeared to look like cut stone and were placed in a man-made structure.
In interviews with the BBC, the exploration team said the layout resembled city streets defining square blocks.
Since then, no conclusion has been drawn - but many theories are currently circulating about the "unexplained" phenomenon. One expert said the site is about 6,000 years old. That's 1,500 years before the Great Pyramid of Giza.
That would challenge current knowledge and suggest that advanced construction techniques were present in the Caribbean long before boffins originally thought possible.
Cuban geologist, Manuel Iturralde, went one step further. In work for National Geographic, he said that the site's depth might point to an age closer to 50,000 years. If true, these structures would predate known human architecture by tens of thousands of years.
However, some suggest this had no human creation and was simply a natural occurrence posing as something more. Iturralde considered this, adding that aging processes like erosion, rock fracturing and sediment build up can sometimes produce shapes that look man-made despite being completely natural.
Back then, however, it was impossible to gain the necessary samples due to lack of technology.
Now, underwater exploration technology has improved so much, the boffins might be able to fill their knowledge gaps more fully.
Experts would take samples for underwater mapping. Then they would look at aspects such as the precision of the shapes, right-angle layouts, the surfaces of the blocks and and pattern that looks like ancient urban planning.
This urban planning is similar to what we might see in modern day cities - but slightly altered for a less progressed society.
Since the last full-scale expedition in 2005, the site has remained largely untouched, but some experts are calling for a second return to the site which many claim could even be the lost city of Atlantis.