Castle of Chios, Medieval fortress and archaeological site in Chios, Greece

The Castle of Chios is a medieval citadel at the northern end of Chios harbour, built of reddish-brown local stone. Its walls form an irregular pentagon with eight surviving bastions, and the eastern side fronts the sea. Inside, a inhabited quarter of about 650 residents surrounds the church of Aghios Georgios Frouriou.

The fortress originated in the 10th century under Byzantine rule and was later controlled by Genoa from 1346 to 1566. The Ottomans then took control and kept the structure for centuries.

The main street of the castle is named after Saint George of the Fortress, whose church began as a 10th- or 11th-century Byzantine building. The Genoese kept a parish church of San Giorgio here, repaired in 1520, and gave its name to a district of the town. Ottoman admiral Piyale Pasha turned it into the Eski (Old) Mosque after 1566; it was rebuilt after the 1881 earthquake and serves again as a church.

The site has multiple entrances, including the Porta Maggiore gate and the Portello entrance to the northwest. Visitors should wear flat shoes and be prepared to navigate stairs and uneven ground.

Just inside the main gate, on the right, lies the Kria Vrisi: a large semi-underground water tank, not a cistern, roofed by vaults forming four quarters divided by a cross and carried on eight shafts. Water was first raised through a large dome-roofed elevated arcade along its eastern side, later through a short cistern at its southeast corner. In 1920 mayor and architect Dim. Tselepidis had it cleaned.