The location of old Istanbul is marked in a triangular shape by the 6½ km-long city wall, called Theodosius II city walls, which started construction in 413. An earthquake in 447 almost destroyed them, so were rebuilt in a hasty two months. The mammoth effort was thanks to 16,000 citizens who were forced to work to get it completed in time to prevent Attila's forces who were fast advancing. They completed construction of the original walls, 5m thick and 12m high, plus and outer wall of 2m by 8.5m, and a moat. Since 1990, some areas have been rebuilt, and some unrestored areas collapsed during the 1999 earthquake. It is possible to walk along the entire length, which would take a full day, with highlights including Yedikule, Edirnekapi and Mihrimah Camii.
At the southern point of the walls is Yedikule and the Golden Gate, the most impressive within the walls. The area is an old, attractive quarter with many churches, since this is the centre of Rum Orthodoxy, the last remaining descendants of the Byzantine Greeks. The Gate is flanked by two marble towers, a monumental entrance through which important state visitors and triumphant emperors would pass through. The gold-plated doors were removed after the collapse of the empire and the entrance bricked up, although the three arches are still visible.
The other five towers were added by Mehmet the Conqueror, and together with the 12m wall it forms the enclave which can be seen today. Two of the towers were prisons, and the one in the second tower was also an execution chamber. The wooden gallows and the well into which the heads would roll, are still visible today, as are some instruments of torture. While the entire enclave was used as a treasury, warehouse and ambassadorial jail, now it is a museum, still with the Golden Gate towers and in the summer months, concerts performed here.
On the Asian side of the Bosphorus, Anadolu Hisari is a small castle built during the 1390s by Sultan Beyazit. Together with Rumeli, on the European side built by Mehmet the Conqueror in 1452, the two fortresses had complete control of passing transport between the Black Sea and the Marmara. Rumeli, an early Ottoman fortress built in only four months, before the Ottoman conquest of the city, to prevent the aides of Byzantine from the north.
Anadolu is always open to explore the walls, and Rumeli has a small open-air theatre showing concerts and plays in summer. There is also a café perched on the top, a popular place in summer evenings for tea, served from great samovars, and light meals. Both fortresses have, of course, a great panoramic view of the Bosphorus.
Anadoluhisarı, Rumelihisarı and Yedikulehisarı