Named for the manner in which it was built (across the water gate into the old Roman fort of Babylon), this 7th-century (or 9th-century, depending on who you believe) Coptic Church is still in use today. It is known more formally as Church of the Virgin. The facade that you encounter as you enter is 19th century and not particularly attractive, but the original interior of the church is charming. The nave is barrel-vaulted, and the inside of the church echoes with the whispers of visitors. The traditional marble pulpit is from the 13th century and is used on Palm Sundays. One of my favorite things in the Hanging Church is the series of 18th-century icons showing the martyrdom of St. George. Kids, meanwhile, will be interested in the window that's been cut in the floor to give a view of the water below.
There are a couple of nice stalls in the entrance to the church where you can purchase books, postcards, and reproduction icons. Another nice thing about this church is that the young men you encounter who offer to show you around are not only knowledgeable but not interested in a tip (though they will be happy to show you where the donation box is).