Images from Istanbul:  Rumeli Fortress

Mehmet the Conquerer built this monumental fortress in preparation of his conquering of Istanbul (Brosnahan 191). Rumeli Hisar was built just across Anadolu Hisar on the Asian shore. The construction of the Rumeli Fortress was completed in about four months (April to August, 1452). The speed was attributed to the impatience of Mehmet. He placed the responsibility of the building of the major three towers in the hands of a vizier. If the vizier did not complete his tower in a specified amount of time, he would have to pay the consequences with his life. Although the architect, Musli-huddin Aga drew the plans for the fortress, his design was under the supervision of the Sultan. The construction of the tower on the seaside was accomplished under the supervision of Vizier Saruca Pasa (28m high, 22.8m wide). Zaganos Pasa supervised the tower in the Southwest (21m high, 26.7m wide). The third tower was under the supervision of Candarli Halil Pasa (33m high, 22m wide). Mehmet personally supervised the construction of all the walls linking the various towers surrounding the fortress.

Apparently, the fortress was successful. It was able to control all traffic on the Bosphorus and cut the city off from supplies from the North. After the conquest of Constantinople, it was used as a tollbooth for a time, then a prison, and later an open-air theater. However, it was never again used as a fortress.