Completed in 1607, Kumamoto Castle is massive. It took 7 years to build, under the direction of Kato Kiyomasa, a great warrior who fought alongside Tokugawa Ieyasu in battle and was rewarded for his loyalty with land. The castle was built atop a hill and had two main towers, 49 turrets, 29 gates, and 18 two-story gatehouses; to make the walls impossible for enemies to scale, they were built with curves at the bottom and nearly vertical at the top and were crowned with an overhang. More than 100 wells ensured water even during a siege, while camphor and gingko trees were planted for firewood and edible nuts. The castle passed into the possession of the Hosokawa family in 1632 and remained an important stronghold for the Tokugawa shogunate throughout its 250 years of rule, particularly in campaigns against the powerful and independent-minded lords of southern Kyushu. During that time, 11 generations of the Hosokawa clan ruled over Kumamoto.
Much of the castle was destroyed in 1877 during the Seinan Rebellion led by Saigo Takamori, a samurai who was unhappy with the new policies of the Meiji government in which ancient samurai rights were rescinded. Saigo led a troop of samurai in an attack on the castle and its imperial troops, who remained under siege for 53 days before government reinforcements finally arrived and quelled the rebellion. When the smoke cleared, most of the castle lay in smoldering ruins.
The castle was reconstructed in 1960 of ferroconcrete, and although it's not nearly as massive as before, it's still quite impressive and remains Kumamoto's star attraction (famous Japanese director Kurosawa Akira used it for his epic drama Ran). The interior houses a museum with elaborately decorated palanquins, models of Kumamoto and the castle during the Edo Period, armor, swords, former possessions of both Kato Kiyomasa and the Hosokawa family, and rifles and other artifacts from the Seinan Rebellion. Beside the castle is a replica of Honmaru Goten Palace, a 17th-century palace that was destroyed in the Seinan Rebellion but has been painstakingly reconstructed using traditional methods. Behind the castle is one of 11 remaining turrets, which is three tiered and five stories. Because the castle grounds are large, you'll probably spend more than an hour here. If you intend to visit Hosokawa Mansion, buy a joint ticket for entrance to both sights (¥640 for adults and ¥240 for children).