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Walls of Constantinople: The Last Great Ancient Fortification

Over the last few years, there has been much discussion over the building of walls. Some see them as vital structures built to defend sovereignty and retain law and order, while others view them as aberrant constructions that do nothing but divide us while aggravating the distance between the haves and have nots.

Whatever your opinions of walls, it’s something we don’t have to think about too much anymore. Except for a few high profile cases, there aren’t many large-scale defensive or dividing walls anymore. The evolution of modern warfare has meant they have become almost redundant. 

But if we were to step back in time, between 1500 and 2000 years ago, there were walls everywhere. And the last great ancient wall, and also one of the most brilliantly complex, was built around the city of Constantinople – now present-day Istanbul. 

Ancient Walls 

As much as the use of walls has become controversial in the modern age, they have been with us almost since day one. The remains of a small wall, probably built to keep out the elements rather than invaders, in the Theopetra Cave in Greece dates back a staggering 50,000 years – at least. 

Theopetra Cave
Theopetra Cave.By Tolis-3kala is licensed under CC-BY-SA

If we want to talk about town or city walls, the city of Jericho, in modern-day Palestine, had a wall around it dating back to 8000 BC and perhaps even further. In Europe, the earliest example of a fortified city wall comes in modern-day Bulgaria, with the ancient settlement of Solnitsata. 

As time progressed walls grew bigger, stronger and far more expansive. The Romans built not one, but two walls across Britain, Hadrian’s Wall – which we’ve already covered on Megaprojects if you’re interested – and the lesser-known Antonine Wall. China is of course the setting of the largest wall the world has ever seen, with the Great Wall of China covering a staggering 21,196 km (13,170 miles).

Like the Roman walls in Britain, the Great Wall of China was built to keep out raiding parties and to defend a mighty Empire behind it, but these types of walls were rare. Much more common were the walls built around specific settlements and again, it was the Chinese that outdid us all. The city walls that once fortified Beijing, Xi’an and Nanjing all stretched to over 20 km (12.4 miles) in length, but all built at between 500 and 1000 years after the subject of our video today, the great Walls of Constantinople. 


The name Constantinople comes with a wonderfully exotic, ancient feel to it. One of those names like Sparta, Alexandria, Carthage, Timbuktu and Machu Picchu that reminds us that great empires and their lavish cities can both rise and fall with dizzying speeds. Like Timbuktu and Alexandria, Constantinople is still very much inhabited today, though under a different name, Istanbul.  

The city, first known as Byzantium, was settled in 667 BC by the Greeks if we are to believe the local legend. As was fairly common back in those days, the city was taken and retaken relatively frequently in the subsequent centuries as the Persians, Greeks and finally, the Romans took their turn to control this important settlement that sat at the division between Europe and Asia.

As the years ticked from BC into AD, the Roman Empire was approaching its peak. Incorporating much of modern Turkey and stretching from the Mauritanian coast (modern-day Morocco) to the border extremities of Britannia (modern Britain), this was an empire of astonishing size, prestige and power. 

But as we know, it all soon began to unravel. I won’t get bogged down over the complex reason why the Roman Empire fell, but let’s just say it came down to over-ambition, social divisions, politics and good old-fashioned climate change. 

With the dawn of the 4th Century AD, Rome was beginning to lose its grip and in 330 AD, Constantine I moved the capital of the Roman Empire from Rome to Constantinople, which was first referred to as Nova Roma, New Rome. The Empire had already been briefly partitioned nearly a century before, but with the death of Constantine I in 337 AD, the empire was again split, this time effectively into four between his three sons and a nephew. What could possibly go wrong?

The subsequent two centuries were nothing if not bloody and chaotic. Rome itself was sacked no less than four times and the western empire eventually completely unravelled, which brings us nicely back to the city of Constantinople towards the end of the 4th Century.

The Earliest Walls

Make no mistake about it, the Roman Empire had taken a series of painful hidings. The once indomitable Roman legions were now being crushed on the battlefield. Their annihilation at the hands of the Visigoths in 378 AD during the Battle of Adrianople, in which the Eastern Roman Emperor Valens was also killed, underpinned the fragility of the situation. To make matters worse, the defeat occurred just a few days march from Constantinople. A decision was made to greatly bolster its existing defences. 

By this point, Constantinople already had two walls of sorts, commonly referred to as the Severan and Constantine Walls. We don’t know a whole lot about the Severan Walls except they were built sometime after the Romans finally gained control over the city in 196 AD. The Constantine Wall was built in 324 AD and was thought to have measured 2.8km (1.7 miles) in length, composed of a single wall with watchtowers located at set distances. It stretched from the Church of St. Anthony at the Golden Horn, southwest and then southwards, to the Church of the Theotokos of the Rhabdos on the Propontis coast. 

But the problem with walls is that they might be good at keeping people out, but they aren’t great at accommodating expansion. By the start of the 5th Century, the city was already overflowing past the Constantine Wall, and with the renewed threat of marauding tribes from the west, it was time to build something bigger. 

The Theodosian Walls

Theodosian Walls of Constantinople, Istanbul
Theodosian Walls of Constantinople, Istanbul.ByCarole Raddato, is licensed under CC-BY-SA

Often when people talk about the great wall of Constantinople, they are talking about the Theodosian Walls. These were a pair of walls that formed one of the most famous defensive structures the ancient and medieval worlds ever saw. Started around 403 AD and finished in 414 AD, the two Theodosian Walls, with one inside the other, measured around 12 km (7.4 miles) in total, although only 5.7 km (3.5 miles) remain today, parts of which have been restored to their full, former beauty and imposing dominance.  

The inner wall was considerably higher than the outer, measuring 4.5–6 metres (14.7 – 19.6 ft) in thickness and 12 metres (39.3ft) high. The core of the wall was constructed using mortar made of lime and crushed bricks, while it’s out section used well-cut limestone bricks. 

It came with 96 separate towers, each between 15 and 20 metres (49-65 ft) tall and between 10 and 12 metres (32 – 39ft) wide. The distance between the towers varies considerably, between 21 and 77 metres (68.8-252ft), which was mostly down to the natural rise and a fall of the terrain. The towers came with traditional battlemented terraces on top, while below the structure was divided into two levels, the first being mainly for storage, while the upper was used by the sentries. 

The outer wall was smaller, stretching to a maximum of 2 metres (6.5ft) in thickness at its base and rising to between 8.5 and 9 metres (27.8 – 29.5 ft). Only 62 of the original towers on the outer wall survive today, but it’s thought it had roughly the same as the inner wall, so almost 100. These towers are slightly smaller than those on the inner wall and are 12–14 metres (39 – 50 ft) tall and 4 metres (13.1 ft) wide. The two walls are divided by an 18.2 metre (60ft) raised terrace with a series of small posterns (an often concealed secondary door) located at the base of the towers connecting the walls and the terrace. 

Around 20 metres (65ft) from the outer wall was another worrying prospect for any would-be attacker, the 20 metres (65ft) wide and 10 metres (32.8ft) deep moat, complete with yet another wall, measuring 1.5 metres (4.9 ft) in height located on the bank closest to the city.  

These four defensive installations provided a fearsome fortification and to make matters worse for invading armies, with the structures all rising steadily from the moat, it must have given the impression of attempting to clamber to the top of a mighty mountain as hell poured down from above. Just to summarize, first, you needed to get across the moat, then over the small. Only then could you begin to tackle two of the best built and best-defended walls in human history. If you’re beginning to wonder whether such defences were ever breached, well, I’m going to leave you hanging there for a little bit longer, but trust me everybody from the Persians, Avars, Saracens, Bulgarians, Venetians, Ottomans and the Russians gave it a hell of a go.  

Sea Walls 

If Constantinople had a weakness, it was probably its proximity to the water, with both the open Sea of Marmara and the Golden Horn Bay flanking the city. Here, two walls were built, although they do meet and together act as the final piece of the broad circular wall system around the entire city. The sea wall that sat opposite the Sea of Marmara was built in much the same way as the land walls, though much lower, it stretched for 8.5 km (5.2 miles) and was said to include 103 separate towers. 

On the other side, facing the Golden Horn Bay, the Gold Horn Wall ran for 5.6 km (3.4 miles) from the Cape of St. Demetrius to the Blachernae, where it met the Land Walls. Today most of the wall is gone, but it’s believed to have measured around 10 metres (32.8ft) in height and built slightly further back from the water in comparison to the other sea wall. It came with 110 towers and also a rather ingenious method to stop enemy vessels from approaching it. A heavy chain or boom was slung out across the bay, composed of floating barrels, which acted as a rudimentary but certainly effective way of blocking ships from entering the bay and approaching the sea walls. 

Evolution of the Walls 

Now, I’m going to stop there with the walls, but believe me, I could carry on. I’ve given you the highlights, but over the years several other smaller sections of walls were added here and there, primarily to strengthen certain sections. The Walls of Blachernae were a series of structures built separately in the north of the city to connect the Theodosian Walls and the Gold Horn Wall. While the Propontis Wall formed part of the Sea Walls, built almost at the shoreline, to a height of between 12 and 15 metres (39 – 49 ft), with 188 towers, and a total length of almost 8.4 km (5.2 miles).

While much of the building work was completed by the end of the 5th Century, there were plenty of additions made to walls over the years, either through the general raising or lengthening or to repair sections after one of the city’s many sieges. 

A Target 

Ironically, it was Constantinople’s famous, imperious walls that seemed to draw would-be invaders to it. Everybody wanted to take down the most feared defensive system in the medieval world. 

By 550 AD, Constantinople had a population of around 500,000, a huge number for that time, but an outbreak of plague decimated the city and that figure fell by roughly 40%. The 5th and 6th centuries saw numerous sieges, first by the Sassanids and Avars in 626 AD and the Persians from 674 to 678 and then in 717 to 718, but the city’s formidable defences held strong, aided in no small part by the introduction of ‘Greek Fire’, which I can only really describe as an early flamethrower that could be used to set fire to enemy ships.

Sporadic violence was never far away, with the Varangians the next up to test Constantinople, but this relatively small-scale attack was repulsed without too much difficulty and as we reached the 9th Century, the city had a population of roughly 750,000 people. 

After sagging fortunes in the 10th Century, the city, and its empire, rebounded with aplomb. Lavish construction projects got underway and all seemed rosy. But success has a habit of drawing envious greedy gazes. The Crusades may have been based on religious ideologies, but the warring parties from Europe, in particular the Latins along with the powerful Venetians, had set their sights on the riches of Constantinople. A foreign-backed coup resulted in a change of emperor in the city, but the chosen successor was himself soon captured and put to death. In response, the vast crusading armies inched towards the city. Constantinople’s famed walls now faced their biggest threat yet. 

By erecting siege towers on their ships, the Latin invaders were able to punch through the sea walls, and on 12th April 1204, the city was finally breached. What came next has come to be known as the Sack of Constantinople, as the city was looted and its population terrorised for three consecutive days before the invaders loaded up their chariots, now growing from plundered treasure, and headed home.   

The coming two centuries were unkind for the citizens of Constantinople as military defeats, civil wars, and natural disasters were compounded by the Black Death, which rampaged through the area in 1347. There was a growing sense that the city was cursed or had been doomed by God. And it was about to get much worse. 

The Fall of Constantinople

In 1453, the Ottomans arrived at the gates of Constantinople where they faced a weary city that at that point had a population of just 50,000 people. By this stage, the Ottomans had already conquered much of the Byzantium territory and they now came with siege artillery for the first time, the most famous of which was a cannon measuring 8.2 metres (27 ft) in length capable of launching a 544kg (1,200-pound) ball over a mile. Quite unbelievably, it came with a crew of 500 and took 2 hours to load. 

The ancient city was facing weapons it was never designed to withstand. The outcome was inevitable, especially as the vast walls and towers were now guarded by just 4,973 Greek soldiers and volunteers along with 2,000 volunteers from the city. The fact that the city held out for seven weeks was nothing short of heroic, but on the 29th May 1453, the Ottomans broke through, and Constantinople finally fell.

The Last of the Ancient Walls  

The great walls of Constantinople may not have been able to withstand the carnage of more modern warfare, but it had repulsed a long succession of attempts to take it at a cost of hundreds of thousands of invading lives. Much of the walls today are gone as Istanbul bustles with chaos and modernity, but if you know where to look you can still see plenty that remains, either as barely recognizable grumbling relics or smartly restored sections that give you a wonderful idea of what it must have been like to approach them all those years ago.   

An estimated 12.5 million tourist flock to the city each year, drawn by its intriguing blend of east and west, of Asia and Europe. Today the doors are flung wide open for foreign visitors, but 1500 years ago you would have been met with the most foreboding set of ancient walls the world has ever seen. These were part of the last great fortification system of antiquity and acted as a bookend to the idea of hiding behind large defensive walls. The walls of Constantinople may have crumbled under modern firepower, but for nearly 1000 years, they were virtually impenetrable.  

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