Kea, resembling a water drop, stands lofty in front of the large sea current Cavo Doro and is considered the natural bridge of communication of the mainland of Greece with the Cyclades, delimiting at the same time the Archipelago from the Southern Eubean gulf. With a perimeter of roughly 85 kilometres and a total surface of 131 square kilometres, Kea is one of the biggest Cycladic islands. Furthermore, Kea is the most western cycladic island and the nearest to Attica.

Its harbour rests only 40 miles from Piraeus and 16 miles from Lavrion. The island is mountainous with medium altitude (285m), the tallest peak being Profitis Ilias (568m) and in-between the mountain ranges narrow valleys take shape. The coasts feature capes as well as sea caverns that are half or wholly under the surface of the sea. The big gulf of Saint Nikolaos, one from the biggest natural harbours of the Mediterranean, is situated at the north-west. While a little more to the east, the gulf of Otzia, that is open to the north is found.

In the south-west, where mountains reach more smoothly to the sea, is located the gulf Koundouros. The villages of Poles and Spathi in the east and Pisses in the west are smaller.