The Theodosian Walls are the landward defences of old Constantinople, the line that closes off the historic peninsula on its western side, from the Marble Tower on the shore of the Sea of Marmara north to the Golden Horn. Both the Ministry of Culture and Tourism and İstanbul Metropolitan Municipality date them to the fifth century and to the Eastern Roman emperor Theodosius II, whose name they carry. Running for about seven kilometres, they lie within İstanbul's UNESCO World Heritage area, and the ministry notes that work on the city walls follows the UNESCO protection programme.
What made the line so hard to take was its depth. An attacker met three obstacles one after another: a moat, then a lower outer wall, and only behind that the main inner wall. Moat, walls and towers together measure about 70 metres across. The inner wall was strengthened with 96 towers, most of them square, placed at irregular intervals to suit the ground. Each tower usually had two rooms that did not connect: a lower one opening towards the city and used for storage, and an upper one entered from the wall-walk, with windows for keeping watch and shooting. The facing is cut limestone crossed by bands of brick, which bound the stone skin to the mortar core and helped the masonry withstand earthquakes.
Earthquakes were in fact the walls' most persistent enemy. Two of them, in 437 and 447, did serious damage, the second destroying long stretches and 57 towers. With Attila's armies in the Balkans, Theodosius II ordered the prefect Constantine to oversee the rebuilding, and Byzantine chroniclers and three inscriptions found on the site say the job was done in sixty days, with the city's chariot-racing teams put to work. Repairs followed again and again over the centuries, recorded in many inscriptions naming the emperors and officials responsible. After the Latin conquest of 1204 the walls were poorly maintained, and in the sieges of 1422 and 1453 the defenders, too few to man both lines, concentrated on holding the outer wall. The walls survived the whole Ottoman period and turn up in the accounts of foreign travellers to the city.
The gates are the best places to read the line. Belgradkapı, near Yedikule between towers 22 and 23, is called the Xylokerkos Gate, the 'wooden circus', in Eastern Roman sources and is thought to have been the most important way in before the Golden Gate was built. After the conquest it was known as the Closed Gate and stayed shut for most of the Ottoman period; it was opened again in 1886, partly so that the Balıklı Greek Hospital could be reached, and its present name is explained either by the neighbourhood that grew up behind it or by people from Belgrade who were settled here after that city was taken in the 16th century. The 1894 earthquake brought down the upper parts of its towers, and İstanbul Metropolitan Municipality restored the gate together with the Taç Foundation in 1986-1987. Further south, the Golden Gate was the ceremonial entrance where the Via Egnatia, the road from Thrace, reached the walls and emperors rode in at the head of triumphal processions; its name comes from the gilded door leaves fitted after a victory in 425, and its two marble towers were later counted among the seven of Yedikule.
In 2020 İBB Miras, the metropolitan municipality's heritage team, began what it describes as the most far-reaching restoration in the walls' history. Its approach, which it calls archaeological restoration, keeps the appearance of a ruin and limits intervention to what structural safety requires, as at Mevlanakapı, the Silivrikapı hypogeum, Edirnekapı and Sulukulekapı. The Mevlanakapı Visitor Centre opened in September 2022 as the first stage and Belgradkapı followed as the second, with a visitor centre for concerts, talks and film screenings and a reference library that opened on 24 February 2024. Alongside the walls, Fatih Municipality has laid out the Karasurları Millet Bahçesi, a public park in stages from Millet Caddesi through Mevlanakapı and Silivrikapı to Belgradkapı, on ground that had been zoned as green space since the early Republic but was built over illegally during the last century; its fourth stage takes in the grounds of Yedikule Fortress.
