In 1601, Yamauchi Katsutoyo became the master of Tosa Domain (Kochi Pref.) and commenced building Kochi Castle on a hill almost in the center of the Kochi Plain. The Honmaru and Ni-no-maru were completed within two years. Further construction and expansion works continued on the San-no-maru and other segments for the following ten years. The castle is a hirayamajiro built on Mt. Otakasaka (approximately 44m above sea level) and the flatlands below it. The Kagami River flowing to the south and the Enokuchi River in the north were used as outer moats. The original tenshu was destroyed by a great fire in 1727, and rebuilt in 1749. The castle was abandoned in 1873 and was spared from WW2 damage. Kochi is the only castle in Japan to have all original Edo period Honmaru structures remaining. Fifteen buildings, including the tenshu, Honmaru Goten Palace, and the Ote-mon, main gate still exist and have been designated as Important National Cultural Properties.