The Fortress of Babylon at old Cairo, within which lies the Coptic museum was erected inside” it, was built by Trajan in 98.B.C. on the river Nile. Doubtless it was smaller than in the next period, because the Emperor Arcadius renewed it and enlarged some parts of it in 395A.D. But some people say that it goes back to ancient Egyptian period. It was also said that the fortress was built instead of the Babylon Citadel which was built by the Persians near here on top of the mountain, and the Arab historians say that the Persians began its architecture then the Romans completed it. Diodorus the historian said: That the prisoners of the war who were captured by Ramses II disobeyed him and occupied the Habnin citadel on the river side towards Memphis to the north; they fought with the provinces nearby and not stop fighting until Ramses gave them their freedom and security. And since they obeyed him and became calm by permitting them to live in the region which they occupied that it be a private colony so they built there a city which they called Babylon, in the name of the capital of their home country.