Ayios Ioannis Cave, the largest in the Cyclades and among the most interesting in Greece, boasts impressive stalactite and stalagmite formations. In mythology, the cave was inhabited by Polyphemus, the one-eyed giant of The Odyssey; the Avelonisia, two rocky outcrops off the island's coast, are the rocks Cyclops hurled at Odysseus.
Merihas, a small bay, is framed by sheer cliffs that rise more than 100 meters above the water. Wild pigeons and buzzards nest in its crevices, making Merihas ideal for bird-watching.
Kastro at Livadi is a fortified defensive tower dating from the Hellenistic period.
The peak of Pappas Hill is the perfect spot for surveying the sea area around Irakleia, offering views to Ios, Paros, Antiparos, Naxos, Donoussa, Ikaria, Makares, Koufonissia, Schoinoussa, Keros, Antikeri, Fidou, Agrilou, Amorgos, Anydros, Anafi, Santorini, Venetiko, and Avelonisia.
Ayios Athanasios an abandoned settlement features fine samples of Cycladic architecture and traditional island town planning.
At Almia Bay, a German hydroplane shot down during the second world war lies on the seabed, about seven meters from the surface. The wreckage is visible from the surface, but also attracts divers and underwater photographers.