You enter through the old Roman gate of Babylon Fortress, its round towers still standing, and the modern city falls away. Your guide walks you to the Hanging Church, named for the way it hangs over the gate's passage, its wooden roof shaped like the hull of an ark. A few steps on is the Church of St. Sergius, built above the cave where the Holy Family is said to have rested, and the Ben Ezra Synagogue, one of the oldest in Egypt. Lunch at a local spot is included. Flat, shaded lanes make this an easy walk.