The prison's outer wall is nearly 20' high and 3' thick. It is comprised of close‐fitting stones. There is only a single opening through the outer wall: the main gate. The main gate is a 10' wide by 15' high opening in the west side of the outer wall. This opening is protected by a heavy iron portcullis. The bars are set a little more than 8" apart. A watchtower sits on either side of the main gate; two guardsmen man each fortified tower, which can be reached only by stairs within each tower, or by traversing the top of the outer wall. The portcullis may be lifted by working a winch in either tower.