This is actually three sights located in one place - a cave where a monk used to live and teach, a small church next to it, and a sea cave with impressive stalactites. The so called hidden school and the very small church of Panagia
Megalomata are located in a cave above the sea, accessible on foot via path near Fakistra
beach. The sea cave of Panagia Megalomata is right below them but you can access it by sea.
There is not much information about the hidden school. According to locals, the monk lived there as a hermit around 17 century and used to teach children how to write and read. The position of the cave is isolated even today - you need to walk about 10-15 minutes on a narrow path which goes down to the sea, as you follow the sign near Fakistra beach. Keep in mind that the last part of the route has a few steep sections covered with boulders but the protective fence will prevent you from slipping away. Once there, you can sit on the few provided benches and enjoy the sea view in silence.
The cave with the hidden school is not deep and you can see it even without entering. The church however is protected with wooden door and you need to bend over so you can enter it - the space inside is small and narrow, with an icon of Virgin Mary, icon-lamp and candles. Just below is the sea cave but you can see only its entrance from above, the access is only from the sea.