Matsumoto Castle in the context of "Himeji Castle"

A moat is a deep, broad ditch dug around a castle, fortification, building, or town, historically to provide it with a preliminary line of defence. Moats can be dry or filled with water. In some places, moats evolved into more extensive water defences, including natural or artificial lakes, dams and sluices. In older fortifications, such as hillforts, they are usually referred to simply as ditches, although the function is similar. In later periods, moats or water defences may be largely ornamental. They could also act as a sewer.

Kumamoto Castle (熊本城, Kumamoto-jō) is a hilltop Japanese castle located in Chūō-ku, Kumamoto, in Kumamoto Prefecture. It was a large and well-fortified castle. The castle keep (天守閣, tenshukaku) is a concrete reconstruction built in 1960, but a number of ancillary wooden buildings remain of the original castle. Kumamoto Castle is considered one of the three premier castles in Japan, along with Himeji Castle and Matsumoto Castle. Thirteen structures in the castle complex are designated Important Cultural Property.