Just south of Areopoli near the village of Pyrgos Dirou are the Diros Caves where you board a small boat and get paddled and punted through some spectacular chambers with fascinating rock formations which are lit to make them look even more wonderous. There is some walking but the boat is the best bit, especially for kids [and me]. The ticket office is on the main road before it bends towards the cave entrance which is rather weird. There is an evocative monument to the local women who drove out invading Ottomans in 1826 near the cave entrance.
It’s all rather touristy of course and your boatman may be friendly or chatty and informative or may be like the one we had last time who was a misery, spoke no English and shot through the caves as fast as possible. Maybe he had an upset tummy and had to be somewhere fast.