The best place to start your tour of the walls is in the Museum Gardens where one of the most important parts of the Roman defences - the Multangular Tower - can be seen. The Multangular Tower was probably built at the command of the Emperor Septimius Severus who ruled the Roman Empire from York from 208 to 211. The tower has 10 sides and is nine metres high. Originally there were three floors on the inside and a roof on top. In Roman times it formed the western corner of the great fortress wall. There was a matching tower at the south corner of the fortress (under modern Feasegate). Long after the Romans had left the Multangular Tower continued in use. The lower part, which has small rectangular facing stones, is Roman while the upper part, identifiable by larger blocks, is medieval. Please use care and common sense when walking the walls. They are a scheduled ancient monument. The steps are worn and there are no railings in places.