Can't come to Kumamoto City without seeing this. It is one of the three most important castles in Japan, it was built by Kiyomasa Kato around 1600. Its main wall is 253 meters in length, making it the longest castle wall in Japan. It was the sight of the samurai's last stand against the Meiji in 1877, a 55 day siege. It is a fascinating place to learn about Japanese history.
Note--part of Tom Cruise's movie "The Last Samurai" was filmed here.