Oval in shape it is the nearest of the Cyclades to the mainland. About 7 miles long and 3 wide.  It host a number a hidden beaches and very good accommodations. You can take a boat from Lavrion which is about 30 miles north of Athens (get there by bus or car) the boat ride is about 2 hours.  Beside the beaches a must see is the Khora the capital of the island that is at its center and whose homes hang from the cliff.  The streets are so narrow you will have to leave your car at the public lot before going into town.