The Babylon Fortress is located nowadays at the Mar Girgis subway station it was built in the era of Emperor Trajan in the second century AD during the reign of the Roman occupation of Egypt, and then it was restored and expanded by the Roman Emperor Arcadius in the fourth century. The thing left from the building is a door flanked by two large towers, on which one of them were built the famous Hanging Church.
The city of the fortress is considered the oldest part of Cairo. It has been built by the Romans on a strategic position to take control of Egypt along the Nile River. The persecution of the Copts in Egypt forced them to take refuge within these forts, where they set up several churches and monasteries inside the fort. And you can during see along the side of the walls the fusion between the Roman and the Coptic architecture.
In fact, this fortress resembles the Roman fortresses in Europe and North Africa from which we understood its construction. The fort is made of limestone and red-stone, the walls of Babylon fortress are 18 meters in height and 3 meters in thickness.