Kos is located in the south-eastern Aegean Sea south of Kalymnos and north of Nisyros at the ancient Keramiko gulf (Kerme Körfezi) or Kos gulf, just 3 nautical miles from Asia Minor coast.

It is the third largest island in the Dodecanese, its extent 290,29 kilometers and its circumnavigation is around 60 nautical miles. From the prehistoric times it was an important channel of the sea ways that started from the Black Sea and along theshoreline of Asia Minor and the islands of Aegean and reached North Africa.