Cow Tower is an historic military tower that stands by the River Wensum in Norwich, Norfolk. It gets its name from the water meadow, once known as Cowholme, in which it stands. It is about 15.2m high, with an internal diameter of 7.3m. The walls are 1.8m thick. It was built in the 14th century and was badly damaged in the rebellion led by Robert Kett, whose men were camped on Mousehold Heath on the other side of the river. The tower is currently closed to the public as the building is fragile, but visitors can walk around it.