A few miles south of Areopolis the ground opens into one of the strangest places in the Peloponnese. The Diros caves are part of an underground river, and about five kilometres of it have been opened to visitors.
How the visit works
You do not walk it. Small boats are punted through the passages by guides who know every low ceiling by heart, and the tour runs between stalactites and stalagmites that come down almost to the surface of the water. The colours in the rock come from rainwater working through the calcium carbonate over a very long time.
The last stretch is on foot. It is cool underground whatever the weather is doing outside, so take something with sleeves.
Why it matters
The caves were used as places of worship in Palaeolithic and Neolithic times, and there is a long tradition connecting them with the underworld. Whether or not you care about that, the scale of the thing is difficult to prepare for.
Getting there
Drive up to Areopolis and continue south. It is an easy half-day from the studios, and worth going early in the season or early in the day, because the boats fill up.
