The cave church Agios Ioannis with its stalactites just below Iraklias’ highest mountain (Papas) is the most important sight of the island of Iraklia. There are actually two caves that are located opposite each other, and one of them has a church bell hanging outside. You can walk to the church from the harbour of Agios Georgios or from the village of Panagia. From Panagia the walk takes about an hour. The Agios Ioannis Cave is the largest cave in the Cyclades. Bring a torch, because there are no lights in the cave. On Papas Hill itself there are spectaculair views across the sea and the surrounding islands.
There are several (remains of) castles on the island Iraklia: in the Bay of Meriha, in Livadi and on Papas Hill. The Bay of Meriha is surrounded by cliffs that are over a 100 meters high.