[KayEyeDoubleDee]

The explorers said they believed the mysterious structures, discovered at the astounding depth of around 2,100 feet and laid out like an urban area, could have been built at least 6,000 years ago. That would be about 1,500 years earlier than the great Giza pyramids of Egypt.

Is this based on how long ago the site would have been above sea level?

[spycatcher]

Explorers View 'Lost City' Ruins Under Caribbean

More discussion in this thread

[Darksheare]

Well... there's a Roman seaport sitting at like 500 feet below sea level. (If memory serves right. It's underwater and National Geographic did a short pictoral about it back in '85.. I think. This is off the top of my head without digging through my magazine piles.) Close to what used to be Herculaneum and Pompeii. The land there rises and sinks because of the magma underground. So it is conceivable that a city is underwater. Now, how far underwater is another thing entirely.