Kea or Tzia as the island is also commonly known, is the westernmost island of the Cyclades group. The port is just 40 miles from Piraeus, making it the closest island the Cyclades group to Athens. There are daily sailings from Lavrion, and travel time is about one hour. There are also boat connections to Syros and Kithnos from the island.

Kea's coast curves into small bays and coves; it's also riddled with sea caves. The expansive Ayios Nikolaos Bay, one of the Mediterranean's largest natural harbors, is on the island's northwest coast while Otzias, on the east, is open to northerly winds. Harbors on the island's northwest are at Koundouros, while there is also anchorage at Poles and Spathi coves on the eastern coast and Poisses on the western coast. The seabed off the coast is carpeted by large fields of marine seagrass or Posidonia.