The first south gate (本丸南ー之門) was a tower gate (櫓門 "yagura mon"). A barbican tower was built on the stone walls to the north and west. This provided a structure whereby arrows could be fired at attacking enemy forces from three sides. The first south gate and the smaller second south gate along with the barbican formed a square, walled castle gate structure called "Masugata Koguchi" (枡形虎ロ). The wall section under the front part of the first gate was covered in wooden tiles, and the gate itself was iron-plated. Rocks could be dropped from a machine on the second store.