Kumamoto Castle is one of the three most beautiful castles in all of Japan. It was built over the seven-year period between 1601 and 1607 by feudal lord Kiyomasa Kato, who used his experience during the Warring States period to design an impenetrable fortress. The walls are curved in the "musha gaeshi" style and are practically impossible for invaders to scale. There are 120 wells, and the trees within the walls are nearly all camphor, which can be used as firewood even when fresh, and gingko, which provides edible nuts. ?The castle's strength was proved during the Seinan War in 1877, when government forces defended against a seige by a rebel army for 53 days. There is a fine exhibition of artifacts related to the castle and the war on display in the donjon. ?Kumamoto Castle is said to be most beautiful in spring, when the cherry trees are in flower, in early summer, when the greenery is at its height, and when the gingko trees turn yellow in fall. The donjon is illuminated with spotlights at night, a sight that delights both tourists and the inhabitants of Kumamoto City. The observation deck of the City Hall across the street provides a splendid view of the castle.