Rumelia Fortress is located on the straightest land of Bosporus, opposite the Anatolian Fortress. Fatih Sultan Mehmet who was embattled to conquer Istanbul observed that Anatolian Fortress was inadequate in keeping the Bosporus under control and had this new fortress constructed. The construction of Rumelia Fortress started in 20th March 1452 and was completed in four months with the effort of 7000 workers and 1800 stonemasons around the clock. Architect of Rumelia Fortress whose timber was brought from Inebolu, stones from quarry around was Muslihiddin.
The fortress which played a great role in conquest of Istanbul lost its importance later and northern Sarıca Pasha Tower became a jail in which many people were locked. So this tower was named as Black Tower.
Rumelia Fortress was located on two steep hills westward onshore. It extends 250 meters in north-south direction and 125 meters in east-west direction. The fortress which consists of three big towers, 13 rows of bastion and the bulwarks combining these has five portcullises. Zaganos Pasha Tower is eight stories and Sarica Pasha and Halil Pasha Towers are nine stories with their basement. Halil Pasha Tower on seashore is 12 cornered. Of other two cylindrical towers Zaganos Pasha Tower is in the south and Sarica Pasha Tower is in the north.
Rumelia Tower which was damaged by earthquakes in 15th century was restored by Fatih the Conqueror between 1460 and 1464, later it was restored in 1510, 1773, 1794 and 1953 again and was converted into a museum in 1970. The garden of this fortress is used as open-air theater occasionally.