The port of Piraeus is the main boarding port for the Greek Islands. However, most of the islands are also served by companies leaving from Rafina port, which has the asset of being located only fifteen minutes away from Athens' airport. If there are no flights available, you can also take the 'flying dolphins' (fast boats), which are a lot less expensive. Though the Greek Islands are all under the same hot sun, none of them is quite alike. In fact, Greece has 9,835 islands, which represent a surface area of about 9,700 sq mi (19% of the Greek territory). Only 115 of them are inhabited (15% of the Greek population). Kastos, the least populated island has about 50 inhabitants, while there are about 540,000 inhabitants in Crete.