It has been said that many of Cairo's residents know little about the Fort of Babylon, though certainly the Christians do, because several of their oldest churches are built into or on its walls. These include El-Muallaqa (the Hanging Church) and the Greek Church of St. George. A number of other Coptic churches are nearby. The area is called Old, or Coptic Cairo (Masr el Atika), for this is indeed the oldest part of the city, and the remains of the fort are Cairo proper's oldest original structure. Indeed, Cairo owes its existence to this fort.

However, the ancient Egyptians were conscious almost from the start that this region, on the borders of Upper and Lower Egypt and originally two independent kingdoms, was the most strategic site in all of Egypt. Of course, ancient Memphis, which was just south of modern Cairo, existed from at least the beginning of the unification of the two kingdoms, and was considered the "balance of the Two Lands".  Though various rulers at different times moved the capital of Egypt to different locations in Egypt, it always seems to have returned to this strategic location. 

In fact, double faced stone implements have been discovered in the gravel beds of the Abbasiya quarter in the northern part of Cairo, indicating that early human activity took place here. However, it is not until the Neolithic period, toward the end of the sixth millennium BC, that we find human settlements near the apex of the delta. 

Yet, by the time of Fort Babylon, human occupation on the east bank of the Nile in this area other than Babylon itself was confined to a bastion, Tendunyas (Arabic "Umm Dunayn"), a cemetery, Heliopolis several kilometers to the north which was then only a small town, and a few monasteries such as that of Theodorus (Dayr Tadrus).

The site's history actually goes back to the beginning of Egypt's history, but we must look to textual references in order to find these roots. When the Nubian ruler, Piye came to Egypt from Napata in the south, we are told that in 730 BC he completed his conquest of the country by taking Memphis "like a cloudburst". He celebrated this victory by traveling to Heliopolis to make sacrifices to the ancient gods, and later by erecting a stela in the Temple of Amun at Gebel Barkal. The stela tells us that, after proceeding eastward out of the ancient capital (Memphis), which simply means he crossed the Nile, "his Majesty proceeded to Helopolis, passing that mountain of Kheraha on Sepa's way, which leads to Kheraha". Sepa was a centipede god and Sepa's way leads through the heart of modern Cairo. 

The ancient town of Kheraha is mentioned once more in his stela as the place where the conqueror made offerings to Atum. Kheraha was situated to the north of Memphis, and is one of actually three pre-Islamic sites that grew up in the general area where Cairo was later founded. Furthermore, it has been conclusively demonstrated that Kheraha corresponds to Old Cairo, which during the Byzantine times was bounded on one side by the fortress of Babylon. The Kheraha mountain is the spur of the Muqattam Hills on which the fortress was built and in ancient times, the Nile lapped almost at the foot of its ramparts.

Kheraha means "battleground", and this refers to one of the oldest Egyptian traditions going back to the Pyramid Texts, which situates an episode of the struggle between Horus and Seth at this location. Hence, the site would have been occupied since the very beginning of Egyptian civilization. We believe that it probably even predates Heliopolis, and that it remained an important city for much of Egypt's ancient history. It was at one time even the capital of the nome (province). There were, during the Arabic period, statues, some colossal, observed in the immediate vicinity of the Roman walls, and they continued to bear witness to the site's antiquity until they were destroyed between the eighth and fourteenth centuries. 

Why the town's name was changed in the first century is a matter of controversy. One view seems to be that the name, Babylon, is derived from a corruption of the ancient Egyptian per-hapi-n-On, which means the House of the Nile of On, which was what the earlier Egyptians called Roda Island. But it is believed that there was an earlier settlement on this site, and Diodorus tells us that this settlement was populated by prisoners whom Sesostris bought from the Mesopotamian city of Babylon, who named it after their own city. When Strabo visited Heliopolis, he notes that, "Going higher upriver, you come to Babylon, a stronghold where a number of Babylonians rebelled and, after negotiations, obtained the kings' permission to settle. Today however it is the garrison town of one of the three legions stationed in Egypt". 

According to tradition, the fort was first built by the Persians in about the sixth century B.C., but at that time it was on the cliffs near the river. When the Romans took possession of Egypt, they used the old fort for a while, recognizing its strategic importance on the Nile, but because of the problems of water delivery, the Roman Emperor Trajan relocated the fort to its present location, which at that time was nearer to the River. Since then, the Nile's course has moved some 400 yards to the north.

By the time of the Arab conquest of 640, the fort was expansive, with forty foot high outer walls and a moat. It had a very successful port, two nilometers and a canal which linked it with the Red Sea. The fortress was accessed by two monumental gates. The first was on the west side, between two big round towers and gave directly onto the bank of the Nile. Today, this is the entrance to the Coptic Museum. Surmounting its northern tower now stand the Greek Orthodox Church of St. George, which echoes the shape of the tower.  The southern tower is now ruined with its internal structure exposed. The second gate, located on the southern side of the fortress, is framed by two semicircular bastions not unlike those at the Roman camp built around the Temple of Luxor. It forms the base for one of Egypt's most famous Coptic churches dedicated to the Virgin Mary and known as Mu'allaqa (the Hanging Church). 

An important element of ancient Babylon was the Ity Canal of Heliopolis, which in the pharaonic era provided a direct link between Kheraha and Heliopolis. It created a lasting impression on Cairo, since its course was later almost entirely adopted for the famous Khalig, which ran alongside the western section of the Fatimid wall, dividing ancient Cairo into two parts. The Ity Canal was initiated by Nekau II in the 26th Dynasty for the purpose of linking the Nile to the Red Sea by way of Wadi Tumilat. It was completed by Darius and renovated by the Greeks. Not always did it branch off from the Nile at the same place, due to the lateral shift of the river's banks. The canal was completely re-dug during the reign of the Roman emperor, Trajan. Almost until the time it was finally filled in 1899, it was opened annually during the Nile Floods with grand ceremonies, which were actually holdovers from the "festival of Sepa" celebrated in antiquity. 

Obviously, Babylon became a Christian stronghold, particularly after problems arose between Western Christians and the Coptics. It became a refuge for these Christians who were persecuted by the Roman Christians of Alexandria.

However, it was almost certainly its strategic location, together with its access to the Nile and the canal, that made the city so important. And it was the fall of Babylon on April 9, 641, following a siege lasting more than six months, that signaled the fall of Egypt to the Arabs under 'Amr ibn al-'As, even more so then the actual fall of Alexandria, the capital of Egypt at that time.

After the archaic city of Fustat was founded just outside the fortress by the Arabs, the fortress continued to be called Babylon for the next century, and in papyrus documents of the period, the names of Fustat and Babylon were used interchangeably. The Arabic place-name was Qasr al-Sham, meaning "Fortress of the Candle", which the area  is still called today

Interestingly, it is only after the Muslim conquest of Egypt that most of the existing ancient churches (and synagogues) of Babylon were built. The Church of St. Cyrus (Abu Qir), which was later dedicated to Saint Barbara's after her relics were brought there from the Mu'allaqa church in the eleventh century, according to some sources may have been founded as early as the fourth century. However, the Muslim authorities gave permission to the Christians to reconstruct pre-existing sanctuaries, as well as for the erection of new churches. For example, the Hanging Church was probably built some fifty years after the Arab Conquest, though Arabic legend attributes it construction to Balthazar, a son of Nebuchadnezzar and a Coptic woman.  

It was from these foundations that one of the greatest cities of the world sprang, from a humble beginning to one of the two largest cities in the world. Today, the ancient fort is almost entirely a Christian enclave, and one of Cairo's most visited tourist sites.