Coming out of the train station Mar Girgis (St. George), you are immediately confronted by the presence of St. George Church, a round Coptic church built on the remains of what was once the northern tower of the Western Gate of an ancient Roman fortress along the Nile. The city enclosed within the walls was known as Babylon. It's unclear exactly why, but one hypothesis is that it means, literally, "Bab il-On," or "Gate of On (the pharoanic name for Heliopolis)."