The mountain-top fortress was built by the Yamato Dynasty (the 3^rd to the 4^th century) to protect its territory. The history is not well known, as it is not described in documents. These days, research and restorations are conducted. We can visit to see the remains of the towers and gates. The view from the west gate is superb. The 2,8 kilometer well-maintained hiking trails are perfect for walkers.