The entire peninsula that descends from Mt. Parnon in the north to Cape Maleas in the south is seismically volatile. Geological upheavals have been so violent in this region, changing the landscape over and over again, as in the case of the rocky islet of Monemvasia, which in antiquity was a promontory that was partly submerged in a strong earthquake.
Even more violent were the upheavals that formed the Petrified Forest south of Neapoli, when the coastline on which a group of palm trees stood was submerged, only to be lifted up again thousands of years later. The fossils of these trees, along with those of other plants and molluscs, are scattered along the coastline below Aghios Nikolaos.
However, the most impressive of all the geological sights in the region – and one of the most beautiful in Greece – is the Cave of Kastania. There are several more caves in the municipality, but visiting these others requires specialised knowledge and equipment.