Next to the remains of an old wall in the center of the photo is the enclosure for the resident ravens. Legend says that the British monarchy will fall if all the ravens leave the Tower, so 7 or 8 ravens are kept as permanent residents by having their wing feathers clipped. They are not confined to the cages, but they're not able to fly over the walls because of the clipped wings. The regular feedings, of course, are made into a speciall event for the tourists.