Kythnos

The island of Kythnos, or, as the locals call it, Thermia, lies between Kea (Tzia) and Serifos, 54 nautical miles from Pireaus.
Administratively, Kythnos belongs to the Kea province of the Prefecture of Cyclades. It has an area of about 100 sq. km. (38 sq. miles) and a circumference of 36 miles. The terrain is rocky with Ai-Lias (336 m.) the tallest pick.
Although Kythnos is not far from Piraeus and Kea, one can find there unexpected peacefulness. Here, too, the terrain is mainly mountainous, but the harshness of the bare earth is relieved here and there by vines or fig-trees like brushstrokes on it, while pretty little bays form indentations in its coastline. There are steep cliffs on the northern side of the island.
The small gulfs which keep the sea peaceful, the white houses, the streets and the old windmills, are some of the attractions of the island. Kythnos is close to Athens, so it is suitable even for weekends.