The Sea Walls Constantinople

The first seaward walls were ordered built by Constantine I along with the main land wall, and enclosed the city on the sides of the Propontis (Sea of Marmara) and the gulf of the Golden Horn (Chrysoun Keras), but scant information survives regarding them. It is very likely, however, that the later walls followed their course. In 439, after the initial enlargement of the city, Theodosius II ordered the then-Praetorian prefect of the East, Cyrus Panopolites, to extend the old sea walls to encompass the entire city.[22] The construction of the walls was similar to, but simpler than, the Theodosian Walls. It consisted of a single wall, relatively low, as no threat was then expected from the sea, where the Roman navy enjoyed undisputed supremacy.
Furthermore, according to Helmuth von Moltke, "the Bosphorus currents and south-west wind (Lodos) made it almost impossible for warships powered by oarsmen or sails to attack." Enemy access to the walls facing the Golden Horn was prevented by the presence of a heavy chain, installed by Emperor Leo III, supported by floating barrels and stretching across the mouth of the inlet. One end of this chain was fastened to the Tower of Eugenius, in the modern suburb of Sirkeci, and the other, in Galata, to a large, square tower, the basement of which was later turned into the Yeraltý (underground) Mosque.

However, after the Arab conquests of Syria and Egypt, followed later by Crete, the naval threat intensified, prompting successive emperors to attend to them. Anastasios II first renovated them in the early 8th century, while Michael II initiated a wide-scale reconstruction, eventually carried out by his successor Theophilos, which increased their height.[23] During the siege of the city by the Fourth Crusade, the sea walls nonetheless proved to be a weak point in the city's defences, as the Venetians managed to storm them.

Following this bitter experience, Michael VIII Palaiologos took particular care to heighten and strengthen the seaward walls after the recapture of the city in 1261, as he faced the further threat of a possible invasion by Charles d'Anjou.

The Propontis Wall

The wall of the Propontis was built almost at the shoreline, with the exception of harbours and quays, and had a height of 12-15 metres, with 10 gates, 3 small gates, 188 towers and a total length of almost 8460 metres, with further 1080 metres comprising the inner wall of the Vlanga harbour. Several sections of the wall were damaged during the construction of the Kennedy Caddesi coastal road in 1956-57.[5] From the Marble Tower to the cape of St. Demetrius at the edge of the ancient acropolis of the city (modern Sarayburnu, Seraglio Point), the wall's gates were:
  • the Gate of St. John Studites (Pylē Agiou Iōannou tou Stouditou), modern Narlýkapý ("Gate of Roses"), which led to the important monastery of the same name.
  • the Gate of Psamathos (Porta Psamatheos, Turkish Samatya Kapýsý), leading to the suburb of Psamathia.
  • the Gate of St. Aemilianus (Pylē Agiou Aimilianou, Turkish Davutpaþa Kapýsý), before the harbours of Eleutherios and Theodosios.
  • the Vlanga Gate (Porta Vlaggas), at the mouth of the River Lycus, within the harbours. It was demolished after the Ottoman conquest, and a new gate (Yenikapý) build in its place.
  • the Kontoscalion Gate (Porta Kontoskaliou, Turkish Kumkapý), at the harbour of the same name.
  • the Iron Gate (Sidēra Pylē), leading to and from the harbour of Sophia or Sophianon (Limēn Sofianōn), also called harbour of Julian (Limēn Ioulianou). In Turkish it is called Kadýrgalimaný Kapýsý.
  • the Bull and Lion Gate (Porta Vōos kai Leontos, shortened to Voukoleōn), which led to the harbour and imperial palace of Bucoleon, in Turkish Çatladýkapý.
  • an unnamed gate, at the southeastern edge of the Imperial quarter, modern Ahýrkapýsý.
  • an unnamed gate, at the southeastern edge of the Imperial quarter, modern Balýkhane Kapýsý (it lies immediately within the later perimeter of the Topkapý Palace).
  • the Gate of St. Lazarus (Porta Agiou Lazarou), at the ancient Temple of Poseidon.
  • the Postern of the Odegetria (Porta tēs Odēgētrias), at the Palace of Mangana, modern Demirkapý.
  • the Postern of Michael Protovestiarius (Porta Mikhaēl Prōtovestiariou), today Deðirmen Kapý.
  • the Eastern Gate (Eōa Pylē) or Gate of St. Barbara (Pylē Agias Barbaras), in Turkish Top Kapýsý, from which Topkapý Palace takes its name.
The Land Walls protected one side of the triangle which was the city of Byzantium. The other two sides looked onto the sea, and were protected by the Sea Walls, which were not as elaborate as the Land Walls, but didn't need to be. In most places, the sea walls consisted of a single wall about 10m - 15m high. There is very little left of this system of walls now.