The island has a north to southwestern direction and is about 12 kilometres (7 miles) long and 6 kilometres (4 miles) wide on average. The coastline is indented with inlets, capes and peninsulas. The southeast and southwest parts have gentler slopes and that is where most settlements and facilities are located.
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 the Persians from invading the mainland and supplying provisions to the army facing the 300 Spartans defending the pass at Thermopylae. The Persian fleet was defeated there at Artemisium and finally destroyed at the Battle of Salamis a year later. Skiathos remained in the Delian League until it lost its independence. The city was destroyed by Philip V of Macedon in 200 BC.
In 1704 monks from Athos built the Evangelistria Monastery, which played a part on the Greek War of Independence as a hide-out for Greek rebels. The first flag of Greece was created and hoisted in the Evangelistria Monastery in Skiathos in 1807, where several prominent military leaders (including Theodoros Kolokotronis and Andreas Miaoulis) had gathered for consultation concerning an uprising, and they were sworn to this flag by the local bishop.
Houses on Skiathos
After the War of Independence and demise of piracy in the Aegean, Kastro became less important. In 1830s, the island's capital was moved to the original site — where it still remains. Today, the ruins of Kastro are a tourist attraction.
During the 19th century Skiathos became an important shipbuilding centre in the Aegean due to the abundance of pine forests on the island. The pine woods of the island were then almost obliterated. This was brought to a halt though, due to the emergence of steamboats. A small shipwright remains north of Skiathos Town, which still builds traditional Greek caiques.
There is a regular boat service to the island and the rest of the Sporades islands with departures from Volos and Agios Konstantinos. The boats are operated mainly by Hellenic Seaways using its high-speed Flying Cat vessels as well as conventional ferries.
Skiathos Island National Airport is at the northeast of the island next to a lagoon and a lowland isthmus separating the island from the peninsula of Lazareta. As of summer 2011, Skiathos airport is served by Olympic Air flights from both Athens and Thessaloniki, while foreign airlines provide charter flights from a range of airports in European countries such as the United Kingdom, France, Austria, the Netherlands, Italy, Cyprus and Scandinavian countries. During the winter 2013/14, work began to expand the airport, with a runway extension and increased hard standing for parked aircraft.