The Student's Lock-Up is fascinating; it's where 19th-century students were held in solitary confinement for various infractions. Back then, if you failed to return library books on time, you'd net two days in the attic; insulting a lady, four days; insulting a (more sensitive?) cloakroom attendant, five days; duelling, up to three weeks. Today one of these rather comfy rooms, with walls covered in original graffiti, is open for viewing.