In 413 A.D., Construction of Constantinople’s triple walls began. Although commonly known as the "Theodosian Walls" after Theodosios II, the reigning emperor), the walls were actually built on the orders of Anthemius, the Empire’s Prefect of the East, to counter an immediate threat from the Huns.
Inside its walls, Constantinople contained some of the most marvellous sights in the civilized world. Many of these reflected the Roman heritage that the Byzantines were carrying on: aqueducts, sewers, public baths, and street planning. Other sights, in particular some 100 churches, reminded one that Constantinople was a very Christian city.
Still other sights reflected oriental influences: the bustling markets offering goods from all over the civilized world, the palace complex of the Boucoleon with its reception halls, mechanically levitating thrones, imperial gardens, and silk factories. Much of the Byzantines' success in dealing with their less sophisticated neighbors was due to their ability to dazzle visitors with such wonders.
The city of Rome was captured by a group called the Goths in 410 and the Western Roman Empire ended completely in 476 AD. However the Eastern Roman Empire survived for a thousand years afterwards. It became the Byzantine Empire.
In conjunction with Constantinople's naturally strong location, the Theodosian walls proved their worth against any number of attacks upon Constantinople through Byzantine history. They fell to an attacking army only twice, once during the chaos of the Fourth Crusade (1204) and, finally, to the Ottoman Turks, who breach them in 1453 with the help of artillery and overwhelming numbers.
The Eastern Roman Emperor Theodosius (408-450) decided to strengthen the defences of Constantinople. He built a great wall across the peninsula on which Constantinople was built about a mile across the west of the city's walls. It was about 15 feet thick and it was strengthened by nearly 160 towers.
The harbor was protected from invasion by a massive chain stretched across its entrance. The landward side had a huge triple set of walls to protect it. Down through the centuries, when all else failed, that chain and set of walls kept Constantinople safe from invasions. Many times all that seemed to remain of the empire was Constantinople itself. But as long as the city survived, the empire also survived to bounce back and recover its old territories.
However the wall proved vulnerable to earthquakes. In 447 when Attila the Hun was pillaging Southeast Europe much of the wall was destroyed by an earthquake. Fortunately Attila was bribed to go away.
However Constantinople finally fell in 1453. The Sultan, Mohammed III had cannons and he used them to good effect. On 7 April 1453 they began firing at the walls. Gradually they chipped away and made breaches in the walls. Finally on 29 May 1453 the Turkish army rushed through the breaches and took the city of Constantinople. The Byzantine Empire came to an end.