Paleokastro is located in the northwest side of Ios (18km from the port) on a hill overlooking Paros, Naxos, Amorgos and the small Cyclades, islands with which it intercommunicated through fire signals. It is a Byzantine castle built for the surveillance of the sea roads that lead to Crete. Nowadays, a short stone paved trail will lead you to the top, where you will see several parts of the walls, ruins of the buildings in the interior of the castle, the gorgeous church of Panagia Paleokastritissa as well as the magnificent view to the blue Aegean Sea.