Walls of Constantinople

The Walls of Constantinople are located in the city of Istanbul, Turkey.
They were built to defend the city of Constantinople between 324-1543 CE, and consist of a double wall and moat.

A single Wall with towers was built by Constantine I (307-337 CE) to protect the new city of Constantinople.
The Theodosian Walls were then built 1.5 miles (2km) to the west of the Constantinian Wall, by the Emperor Theodosius I (402-450 CE).
The Theodosian Wall consists of a large inner Wall with originally, 96 Towers, below it a smaller outer Wall, and in front of that, a moat which was 65 foot (20m) wide and 32 foot (10m) deep.
Despite attacks, earthquakes and floods, the Walls stood firm until 1453 CE, and only fell with the arrival of the cannon.
The Walls have been restored and can be visited today.

The Anastasian Wall, also known as the Long Walls of Thrace, was a north-south 35 mile (56km) stone and turf wall that ran from Evcik Iskelese in Catalca on the Black Sea to a few miles west of Silivri on the Sea of Marmara.
It was built between 507-512 CE by the Eastern Roman Emperor Anastasius I (491-518 CE) to protect Constantinople from invaders from the west and is located 40 miles (64km) to the west of Istanbul in Turkey.