The island has roughly rhomboid shape, elongated in southwest-northeast direction. The longer diagonal is about 12 km long, and the island is about 6 km wide in average. The coast is interspersed with numerous inlets, capes and peninsulas.
The terrain is hilly, more rugged on north, and the highest point is at the altitude of 433 m. Southern and southeast parts have gentler slopes, and most of settlements and facilities are located there.
The main road runs along southern and eastern coast of the island, with several smaller and dirt roads reaching the inland and northern coast. The town of Skiathos and the airport are located at the northern part of the island’s eastern side. Tsougria and all other main islets are located a few kilometres off the eastern coast, and are visible from the town.[
Much of the island is forested. The area around the villages and the town are farmland. The island’s forests are pine and are concentrated in the southeastern part of the island. The island of Skopelos can be seen from Skiathos with the more distant islands of Euboea and Skyros also visible in clearer conditio
In Ancient times, the island played a minor role during the Persian Wars. In 480 BC, the fleet of the Persian king Xerxes was hit by a storm and was badly damaged on the rocks of the Skiathos coast. Following this the Greek fleet blockaded the adjacent seas to prevent naval invasion and provisions for the enemy of 300 Spartans who stood heroicaly at Thermopylae pass. Persian fleet was defeated there Artemisium and finally destroyed at the Battle of Salamis a year later.