Olous City, Crete
Off the shore of the fifth largest island in the Mediterranean lies an old, abandoned city. Olous City was a powerful city-state in its time with its own harbor and coinage. The sea swallowed this city due to an earthquake sometime in the 2nd century AD. Today, visitors can explore the ruins and partially collapsed structures that sit on the bottom of the ocean floor. It’s a fascinating glimpse into the past. This area should only be explored while snorkeling because you can’t see much from the surface of the water.