Dia is 5 km long and 3 km wide and covers an area about 12 sq km, extending from west to east. North of the Dia, there are two islets with gulls, Paximadi and Petalidi. In the southern part of the island there are 4 quiet bays: the gulf of St George, which is the only port of the island, the Gulf of Kapari, the bay of Panagia and the Gulf of Agrielia. On the east, there is the Gulf of Aginara. The island has a maximum height of 220 meters and the landscape is generally characterized by stones and shrubs. There are areas with rocky cliffs that reach 60 meters.