Went and had a look at Monasterio de Santa Catalina today, a 400-year-old monastery and convent in the middle of Arequipa. Apparently, it's the only monastery in the world that's considered to be "a city inside a city". It's also still fully functioning, and inhabited by the same order of nuns that began it in Renaissance times. Interesting to see the antique sleeping rooms, the beautiful architecture, and — bizarrely — the ingenious laundry system that they have inside. Worth a wander, if you're in Arequipa and have an hour or so to spare.