Kythnos is an island in the Western Cyclades between Kea and Serifos. It is 56 nautical miles (104 km) from the port of Piraeus and 2 hours from the port of Lavrio. It is also called Thermia, at least since the 12th century, when it is referred to as "Diocese of Kea and Thermia". This name is due to the existence of hot springs, which are located in the bay of Loutra.

It has 92 coves, coves and beaches, most of which are accessible by road. There are two villages on the island, Chora or Mesaria, which is also the capital of the island, and Dryopida. In addition, there are three main coastal settlements: the main port of Merichas the Baths with the thermal springs and Panagia Kanala with the homonymous church. This area of ​​Kanala is one of the most popular summer destinations as many tourists vacation there. It is also famous as the most "green" place on the island.

Apart from them, there are several smaller settlements such as: Naoussa, Ag. Dimitrios, Episkopi, Ag. Stefanos, Flampouria, Kalo Livadi, Ag. Irini and Apokrousi.