The flooded caves of Diros, inhabited since Neolithic times, lie 11km south of Areopoli in the Greek Peloponnese. Abandoned as a human habitation in 4 BC after an earthquake, the caves weren't rediscovered until around 1895. Then in 1949 the local husband-and-wife speleology team of Anna and Yiannis Petrocheilou began to systematically explore the caves, now estimated to be around 14km long. Underwater exploration continues to this day and tourism is well developed where boat-tours are very popular.