The municipal museum sits beneath the castle's northern walls and gives a clear, well-laid-out introduction to Kumamoto's history, archaeology, and natural environment. Highlights include a planetarium under a small dome, a section on the Aso volcanic plateau, and a long display on the 2016 earthquake that gutted the castle.
Worth an hour before or after the castle. Captions are bilingual on the main exhibits. Closed on Mondays and through the new year.