Late Roman & Byzantine Sites of Istanbul

Part Two: Fortifications


Constantinople had multiple land walls throughout its history.


Wall of Byzantium

7th or 5th century BC

The first wall protected the city when it was known as Byzantium. The acropolis of the Greek city was located in the area of today’s Topkapı Palace and Gülhane Park, and the wall ran in its immediate vicinity. It is not known if that wall dates back to the foundation of the city by Byzas in around 657 BC or was built by the Spartan general Pausanias after his conquest of the city in 479 BC.


Severan Wall

Late 2nd or early 3rd century

The original wall was destroyed in 196 AD, when Roman Emperor Septimius Severus captured the city. Convinced by his son Caracalla to rebuild the wall, Septimius Severus moved the western wall a few hundred metres westwards, thereby more than doubling the size of the city. The Severan Wall probably ran from near the modern Galata Bridge to the vicinity of the Nuruosmaniye Mosque and from there to the southern wall of the Hippodrome, to meet the old wall near the Bosphorus in the northeast.

By the beginning of the 4th century the city may have expanded beyond the Severan Wall, and there may have been a pre-wall further in the west. No remains of these earlier walls exist.


Constantinian Wall

Early and mid-4th century

In the 320s, Emperor Constantine the Great started to realise his plan to turn Byzantium into New Rome, his new capital. This also meant the construction of a new city wall.

His wall migrated 2.8 km westwards from the Severan Wall, and the area enclosed by it was perhaps four or five times as large as it had been in the Severan era. It included the vast area of the city’s old cemeteries, located in a triangle between the modern quarters of Beyazıt, Laleli and Süleymaniye. It began near the modern Atatürk Bridge, ran southwest and then south, until it ended on the coast of the Propontis.

Constantinian Wall was a single wall with towers at regular intervals. Work on it was completed during the reign of Emperor Constantius II (337-361).

By the early 5th century, the city had expanded outside the this wall. The Constantinian Wall survived later, even though not any more as the primary defense. A section of its foundations was discovered during the construction of Yenikapı Transfer Centre.


Theodosian Walls

Inner wall – 404-413; outer wall and moat – after 448; many later repairs, renovations and reconstructions

The fourth land wall, located around 2 km westwards from the Constantinian Wall, was constructed in two phases.

The first phase began in 404-405, during the reign of Emperor Arcadius, and ended in 413, during the minority of Theodosius II. The structure built forms the inner layer, or the Great Wall, of what become to be known as the Theodosian Walls. It is a single curtain wall, interspersed with 96 towers (mostly square towers). It is 4.5-6 m thick and 12 m high, the towers being 15-20 m high. Its core consists of mortar made of limestone and crushed bricks, and it is faced with carefully cut pieces of limestone. Horizontal bands of brick traverse the wall, not just as a form of decoration, but as a means of strengthening the cohesion of the structure, as these bands help to bond the stone and the mortar and also provide resistance to earthquakes. Only some of its towers that we see today are original. Most of them were rebuilt in the later Byzantine or Ottoman times.

Tower of the Great Wall north of the Gate of Saint Romanus


Great Wall south of the Fifth Military Gate


Great Wall south of the Gate of Pege


Great Wall north of the Gate of Xylokerkos



The Great Wall was damaged in earthquakes in 437, 447, and 448. Its repair was ordered by Theodosius II immediately after, considering the threat posed by Attila the Hun from the Balkans. It is probably at this time that the lower outer wall, or the Small Wall, and the moat in front of it were added. The outer wall is 2 m thick at its base and is crowned with a battlemented walkway, reaching a height of 8.5-9 m. Its towers are situated approximately midway between the inner wall’s towers, acting in a supporting role. 62 of these towers survive. They are 12-14 m high, and their ground plan is either a square or a semicircle.

The terrace between the inner and the outer wall was called peribolos. Between the outer wall and the moat was the parateichion. The moat was about 20 m wide and 10 m deep. It had a crenellated wall on the inner side, reaching about 1.5 m above the parateichion and serving as the first line of defense.

Theodosian Walls near the Gate of Saint Romanus



Theodosian Walls north of the Fourth Military Gate



Theodosian Walls north of the Gate of Rhesios


Theodosian Walls south of the Gate of Pege


Theodosian Walls north of the Gate of Xylokerkos



Theodosian Walls south of the Golden Gate


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The Theodosian Walls were pierced by nine gates and a number of posterns. The gates are traditionally divided into two: public gates and military gates.


11. Golden Gate

The Golden Gate, or the Porta Aurea, was the first gate in the Theodosian Walls from the south. It was the most important gate of the fortification. It served as the main ceremonial entrance to the city, used by emperors on the occasions of military victories. On August 15, 1261, Michael VIII Palaiologos entered the recaptured city through this gate.

With its large square blocks of polished white marble, large towers on its both sides, and its three arched entranceways, the middle one being larger than the other two, the Golden Gate looked like a real triumphal arch. It was also richly decorated with statues, including one of Emperor Theodosius I (379-395) on an elephant-drawn quadriga on top, echoing the Porta Triumphalis in Rome.


The Golden Gate gate was hugely influential in the Orthodox world, with cities such as Thessaloniki, Antioch, Kiev, and Vladimir naming their principal entrances after it. Entrance to the San Francisco Bay in California and the bridge spanning it have been named after it as well.

In 1458, Sultan Mehmed the Conqueror built a fort on the site of the Golden Gate, adding three larger towers to the four existing towers on the Great Wall wall, thus forming the Fortress of the Seven Towers, or the Yedikule Fortress. The Golden Gate lost its function as a gate. For much of the Ottoman era, it was used as a treasury, an archive, or a prison.


12. Gate of Xylokerkos

The name of this gate derives from a wooden circus, located nearby outside the walls. It is now known as the Belgrad Kapısı, after a later settlement of Serbs in the area.






13. Gate of Pege

Another important gate was the Gate of Pege (Gate of the Spring). It was named after a holy spring located outside the walls (Monastery of Saint Mary of the Spring, or the Zoödochos Pege). It was through this gate that the forces of the Empire of Nicaea, under General Alexios Strategopoulos, entered and retook the city from the Latins on July 25, 1261.

This gate was extensively rebuilt in later Byzantine times. The gate arch is Ottoman. It is known as Silivri Kapısı in Turkish.





14. Gate of Rhesios

The best-preserved of the gates, retaining substantially its original, 5th-century appearance, is the Gate of Rhesios (now Yeni Mevlevihane Kapısı). It was named after a general of ancient Byzantium, though in other sources it is called the Gate of Rhegion, allegedly named after the suburb of Rhegion (today’s Küçükçekmece).





15. Fourth Military Gate

The Fourth Military Gate is located between the Gate of Rhesios and the Gate of Saint Romanus.



16. Gate of Saint Romanus

The second largest gate after the Golden Gate was the Gate of Saint Romanus, named after a nearby church. It is known in Turkish as Topkapı, or the Cannon Gate, after the great Ottoman cannon that was placed opposite it during the 1453 siege. It was here that Constanine XI Palaiologos, the last Byzantine emperor, was executed on May 29, 1453. Some don’t favour this gate as the site of execution of Constantine IX, favouring the Fifth Military Gate instead.


Relief of lions on a wall of the tower adjacent to the Gate of Saint Romanos



17. Fifth Military Gate

The Fifth Military Gate, located north of the Lycus River, is named after the quarter of Pempton. In Turkish it is known as Sulukulekapı.




18. Gate of Charisius

The most important gate in the Theodosian Walls after the Golden Gate was the Gate of Charisius. It was named after a monastery, but later it was also known as the Gate of Adrianople (Edirnekapı). It stands on top of the Sixth Hill, the highest point of the old city with its 77 meters. It is from here that Mehmed II made his triumphal entry into the city on May 29, 1453. It was the only time in the history that the Theodosian Walls were breached.



Inscription of Manuel Palaiologos Iagaris from the land walls in Edirnekapı
(possibly from the first half of the 15th century; Istanbul Archaeology Museum)4c


The Theodosian Walls are widely considered to be one of the most elaborate fortification systems ever built. They were the last great fortification system of antiquity, and they allowed the city and its emperors to survive for more than a millennium, against all strategic logic.

The walls remained largely intact during most of the Ottoman period. Sections of them were dismantled in the 19th century, as the city grew out of its medieval boundaries. Some sections have been virtually rebuilt, with no regard for ancient stonework and conservation principles.


19. Byzantine Gardens

Behind the Theodosian Walls are vegetable and fruit gardens that date back to the Byzantine period. Even though the gardens of Constantinople, lying both inside and outside the walls, were mostly destroyed after 1453, the farming tradition in some parts of the walls continued largely uninterrupted through the Ottoman Empire into the modern Turkish Republic. This is especially visible near the gates in the south, where the gardens produced famous buttery lettuce as late as in the 20th century. Today a lot of gardens can be seen here as well.

Vegetable gardens along the Theodosian Walls north of the Gate of Xylokerkos



Vegetable gardens along the Theodosian Walls south of the Gate of Rhesios



A part of the fortification system of Constantinople was the Anastasian Wall 56 km to the west of the Theodosian Walls. It is named after Emperor Anastasius I Dicorus (491-518), but it probably existed already in during the reigns of Emperors Leo I the Thracian (457-474) and Zeno (474-475, 476-491). It was 3.30 metres thick and over 5 metres high, and it was endowed with towers, gates, forts, and ditches. Its was a pre-wall, the first line of defense against invasions from the west. Its effectiveness, however, was limited, and it was abandoned in the 7th century.

Between the Anastasian and Theodosian Walls were several towns and fortresses. A major military encampment was in Bakırköy, known as Hebdomon, or the Seventh, in Byzantine time, because of its distance in Roman miles from the Milion, the zero-mile marker of the empire. Several localities along the main routes to the city served as outer defenses of the city.


Walls of Blachernae

In the 4th century, when Constantinople was still bordered by the Constantinian Wall, Blachernae was outside the city limits. It had its own wall, which formed a triangle, with the points being the later Palace of the Porphyrogenitus, the Prison of Anemas, and the Church of Hagios Demetrios Kanabos. Its western section was later connected to the Theodosian Walls, while the eastern sections fell into disrepair.

The exact course of the Theodosian Walls in this area is difficult to ascertain, as they burned down during the siege of Constantinople by Avars and Persians in 626. Today, nothing is left of them. Some ruins of a limestone wall of different quality can be found southeast of the Church of Hagios Demetrios Kanabos. It has been suggested that this is a surviving section of the Theodosian Walls in Blachernae, but this is not universally accepted.

The Theodosian Walls end at the Palace of Porphyrogenitus. The walls that follow to the north are from different periods.



20. Wall of Manuel I Komnenos and Gate of Kaligaria

Mid- and second half of the 12th century

At the Palace of Porphyrogenitus, where the Theodosian Walls end, begins a short wall which ends with the first tower of the wall built by Emperor Manuel I Komnenos (1143-1180). The latter wall begins at an almost right angle from the line of the Theodosian Walls, goes westward up to the third tower and then turns sharply north. It was built to protect the Palace of Blachernae, the emperors’ preferred residence since the late 11th century. Built with masonry, thicker than the Theodosian Walls and consisting of a series of arches on its outer side, it is architecturally an excellent fortification. Because it runs over the Sixth Hill, which has a steep western slope, it lacks a moat. It resisted the final Ottoman siege, despite repeated attacks and intensive bombardment.



The wall of Manuel I Komnenos contains one gate, the Gate of Kaligaria, or ‘the Gate of the Sandal-makers’ (Eğri Kapı in Turkish).



From the last tower of the wall of Manuel I Komnenos to the Prison of Anemas stretches a 150-m wall with four square towers. It is of a markedly inferior quality and is probably from a later date.


21. Prison of Anemas

12th century

The Prison of Anemas is part of the land walls. It was named after a general who rose against Emperor Alexios I Komnenos (1081-1118). He was also the first person to be imprisoned here. Several emperors were later imprisoned here as well.

The prison consists of two towers and a horizontal structure.

The towers stand side by side. The shorter tower, known as the Tower of Anemas proper, dates from the beginning of the 12th century. It is a well-built structure, with carefully alternating layers of stone masonry and bricks. The higher tower, the Tower of Isaac II Angelos, was built at the end of the 12th century, during the reign of the emperor after whom it is named. It has a bad architectural quality, largely because it was made of diverse materials from ruined churches. It is notable for the arched windows of its upper floor, which indicates that the building may have also been used as a private residence.



The horizontal structure consists of two walls that are divided by buttress-walls into 12 compartments. One wall had corridors running on its upper two floors. The role of the compartments is unclear. They have been identified as prison cells, but they may have also functioned as storage rooms or barrack rooms. The latter hypothesis makes the structure a more integral part of the defensive wall.



22. Walls of Heraclius and Leo V the Armenian

Wall of Heraclius – first half of 7th century, reinforced in second quarter of 9th century; wall of Leo V the Armenian – early 9th century

After the Prison of Anemas comes a double wall. The inner wall is of unknown origin. It may be a surviving section of the original Theodosian Walls, which burned down in 626, but it is more probable that it was built by Emperor Heraclius (610-645) right after it, to protect the Church of Saint Mary of Blachernae. This wall was renovated and strengthened by Emperor Theophilos (829-842), who added three fine hexagonal towers, each of which is pierced by a gate, together forming the Gate of Blachernae.

The outer wall was constructed by Emperor Leo V the Armenian (813-820) to safeguard against Bulgarians. It was extended to the south by Emperor Michael II (820-829). This wall is a relatively light structure (less than 3 m thick), has four towers and is buttressed by arches that support its parapet.

The two walls formed a fortified enclosure, known as the Pentapyrgion (‘Five Towers’) in Greek in the Ottoman era (cf. Yedikule). It connects the land walls to the sea walls on the side of the Golden Horn.


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There was also a short wall at the northernmost end of the land walls, at the Golden Horn. It was built in the 9th century, and it was demolished in the 19th century. It was pierced by the Wooden Gate (Xyloporta), which gave name to the entire neighbourhood.


Sea Wall

Mid-5th century; substantial renovation in 9th century; many other repairs, renovations and reconstructions

Both Greek and Roman Byzantium are thought to have had sea walls. When Constantine the Great constructed his land wall, he is said to have built the sea wall together with it.

The first actual reference to the construction of the Sea Wall comes from 439, when Theodosius II ordered Cyrus of Panopis, the praefectus urbanus, to repair the land walls and complete them on the seaward side. This order was made considering the growing naval threat of the Vandals, who had conquered Carthage earlier in the same year.

The Sea Wall enclosed the city on the sides of the Golden Horn and the Sea of Marmara, known as the Propontis in the Byzantine era. On the side facing the Golden Horn it was located in a slight distance from the water, while the Propontine Wall was at the shoreline. It was architecturally similar to the Theodosian Walls, but simpler. It was lower than the land walls, and it was a single wall, with extra circuits in the locations of the harbours.

The Sea Wall was renovated in the early 8th century, either under Emperor Tiberios III (698-705) or Anastasios II (713-715), as a precaution against the naval threat posed by Arabs. Emperor Leo III the Isaurian (714-741) installed a heavy chain or boom, supported by floating barrels, across the mouth of the Golden Horn, to prevent the access of enemies to the walls. Its one end was fastened to the Tower of Eugenios in today’s Sirkeci, while the other was attached to a tower of a fort in Galata, located on the site of today’s Underground Mosque. (A similar structure to close off the Bosphorus was later planned by Emperor Manuel I Komnenos, but it is not known if that plan was actually realised.)

Portion of the iron chain used to close off the entrance to the Golden Horn
(Middle Ages; Istanbul Archaeology Museum)


Michael III (842-867) initiated a wide-scale reconstruction of the Sea Wall, completed Theophilos (829-842). The latter’s extensive work basically meant the rebuilding of the wall.

The Sea Wall was a weak point in the defense of Constantinople during the siege by the Crusaders in 1204, and the Venetians managed to storm it. It was the only time in the history of the city that the Sea Wall was breached.

After the reconquest of the city in 1261, having in mind the presence of the Genoese in Galata across the Golden Horn, Emperor Michael VIII Palaiologos heightened the Sea Wall. A second wall was built behind the original wall a decade later, because of the threat of invasion posed by Charles d’Anjou, King of Sicily.

Today the Sea Wall of Constantinople exists only partially. No remains of the inner wall exist.


Golden Horn Wall

Almost the entire Sea Wall facing the Golden Horn has been demolished. Some portions of it survive in Cibali, Balat and Fener, but are in a very bad condition, often being incorporated into later buildings.

There were a number of gates on this side of the Sea Wall.

The gates in the Blachernae quarter should be mentioned because of their connection to the contemporary and later churches. One of the first gates, the Gate of Saint Anastasia, was located near the churches of Hagia Thekla and Hagios Demetrios Kanabos.

Further in the east was the Palace Gate (Balat Kapı), which consisted of three gates, serving either as entranceways to the shore or to a harbour that serviced the imperial Palace of Blachernae. Sometimes the name Balat Kapı is used to refer to one of these three gates. Other two gates that existed around here were the Kynegos Gate (Gate of the Hunters) and the Gate of Saint John the Forerunner and Baptist.

Marble relief of Nike bearing a date branch, which decorated the entrance of the Palace Gate (6th century; Istanbul Archaeology Museum)


Further south-east was the Petrion Gate, named after an important official during the reign of Justinian. It was through this gate that the Venetians entered the city in 1204. Then came the Gate of the Phanarion, named after a light-tower, which gave its name to the entire neighbourhood. Between these two gates, formed by a double stretch of walls, stood the Petrion Fort.

The Gate of the Neorion, situated around the later New Mosque, led to the Neorion, the main harbour of the old Byzantium and the oldest naval arsenal of the city. To its east was the bigger Prosphorion Harbour. Immediately to its west were the trading quarters of the Genovese, the Pisans, the Amalfitans, and the Venetians. A quarter allocated to Muslims (together with a mosque) was on the southern shore of the Golden Horn as well.


Propontine Wall

The Sea Wall facing the Marmara Sea got damaged in the late 19th century, during the construction of the railway to Sirkeci, and again in the 1950s, during the construction of the Kennedy Caddesi. Long impressive sections of it still survive.

On the promontory separating the Golden Horn from the Sea of Marmara was the Gate of Saint Barbara. It was unique among the sea gates, being flanked by two large towers of white marble, like the Golden Gate in the Theodosian Walls. It served twice as the entry point of the emperor’s triumphal return (in 1126 and 1168). In Turkish, it is known as Top Kapısı (the Gate of the Cannon), from which the Topkapı Palace takes its name.

Section of the Sea Wall near the Topkapı Palace

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The Mangana quarter in the south, named after an arsenal, was home to the Palace of Mangana and the Monastery of Hagios Georgios Mangana. The Monastery of Panagia Hodegetria, which housed one of the most important icons of the city, was also here, as was the Monastery of Christ Philanthropos.

Section of the Sea Wall south of the Pearl Pavilion


A notable gate in the Propontine Wall is what was called the Ahır Kapısı, or the Stable Gate, in the Ottoman times. It led to the stables of the Topkapı Palace. Its Byzantine name is not known.

Ahır Kapısı


The gate of the Palace of Boukoleon was known as the Gate of the Lion, named after the marble lions that flanked its entrance. West of it was the Gate of the Bear, named after the depiction of a bear. It is known in Turkish as the Çatladı Kapı (the Cracked Gate), because of damage caused by an earthquake in the 16th century.

Further to the west, after two smaller harbours, came the Jewish Gate (Yenikapı) and the area known as Vlanga.


23. Harbour of Eleutherios / Harbor of Theodosius

Northeastern end of Nadir Nadi Park, Kocamustafapaşa
Reign of Theodosius I (379-395)

Next to the Jewish Gate was the large Harbour of Eleutherios, or Harbour of Theodosius. Constructed during the reign of Theodosius I (379-395), it was the most important harbour of Constantinople in late antiquity. Attack against the city from this side was almost impossible, because of the strong currents of the sea. The wall, however, had to be protected against the sea itself. Thus, a breakwater of boulders was placed in front of the base of the wall, and marble shafts were used as bonds in the base, to enhance structural integrity.

Sea Wall at the Harbour of Eleutherios


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To the west of the Harbour of Eleutherios was the Gate of Saint Aemilianus (now Davutpaşa Kapısı), which may have stood at the junction with the Constantinian Wall. Then the shoreline turns sharply southwest. Here we find the Gate of Psamathia and a Byzantine gate known in Turkish as Narlıkapı, or the Pomegranate Gate, which lead to the famous Monastery of Stoudios.


24. Tower of Basil and Constantine (Marble Tower)

Kennedy Caddesi & Genç Osman Caddesi, Yedikule
Before the 11th century

The Sea Wall joined with the Theodosian Walls at the Marble Tower, or the Tower of Basil and Constantine. Because this tower was made of a special material, it might have also had a special owner.



One should not forget the Yoros Castle when talking about Byzantine fortifications in Istanbul.


25. Yoros Castle

Tuna Caddesi 5, Anadolu Kavağı
After 1261

The Yoros Castle is a late-Byzantine castle located in the village of Anadolu Kavağı. It stands at a highly strategic position at the confluence of the Bosphorus and the Black Sea, at one of the narrowest sections of the Bosphorus. This area was used for military and trading purposes already by Phoenicians and Greeks. Remains of ancient temples have been been found here. The name of the castle may come from one of these temples, dedicated to Zeus Ourios (Zeus, Granter of Fair Winds). The Greeks called the area Hieron (Sacred Place), a name which could, again, explain the name of the castle. Yoros may also come from the Greek word ‘oros’ (mountain), as the castle is located on a hilltop.

The castle was intermittently occupied during the Byzantine Empire. It is not clear, when the current structure was built. It is usually assumed that it dates from the Palaiologan period, as the motto of the ruling dynasty – a cross surrounded by four B’s (B for ‘basileus’) – can be found on an inside wall above the entrance. The castle formed a couple with another fortification, located on the opposite shore of the Bosphorus, in Rumeli Kavağı. It is known that a massive chain was extended between these two castles, to cut off the straits to attacking warships (like the chain that crossed the Golden Horn and, possibly, another chain located at the southern end of the Bosphorus).


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The Yoros Castle was conquered in 1305 by the Ottomans, but it was soon retaken by the Byzantines. In 1391, the Ottomans conquered it again and used it as a field headquarters during the construction of Anadoluhisarı, a castle built for the eventual capture of Constantinople. In 1399, the Byzantines attempted to reconquer the castle, but with no luck. In 1414, the Genoese took it from the Ottomans. They were driven out by Sultan Mehmed II after the conquest of 1453. He fortified the structure and added a customs office, a quarantine and a checkpoint. Bayezid II (1481-1512) added a mosque within the castle walls. In the early 17th century, the castle had an important role in securing the Bosphorus against the raids by Cossacks.