The Rumeli Fortress sits on a hill on the European side of Istanbul, overlooking the Bosphorus at its narrowest point. Built by Sultan Mehmed II prior to the conquest of Constantinople, the fortress was intended to help him control traffic along the Bosphorus and prevent aid from reaching the city from the Black Sea during the Siege of Constantinople in 1453. With the help of thousands of workers, the fortress was completed in just over four months.
In addition to three main towers, the fortress had one small tower and thirteen watchtowers, as well as three main gates next to the three main towers. It also had wooden houses for soldiers, a small mosque and a large cistern that distributed water to the fortress through three wall fountains. The shaft of the mosque’s minaret and one of the water fountains remain in the fortress today.
After the conquest of Constantinople, the fortress served as a customs checkpoint before later becoming a prison for foreign prisoners-of-war. It was completely abandoned by the 19th century, allowing a residential neighborhood to pop up inside. In 1953, Turkish president Celal Bayar ordered the residents to be relocated so the fortress could be renovated. It reopened as a museum and open-air theater in 1960 and as functioned as such ever since.