Azuchi Castle Ruins, located in Omihachiman City, Shiga Prefecture, is the site of a castle built by Oda Nobunaga as a base for unifying the country. This castle, which is said to have been built in just three years, was a huge seven-story structure with a "tenshu" (castle tower), which was innovative for its time. Unfortunately, the tenshu no longer exists, but the stone walls and foundation stones that remain today give a glimpse of Nobunaga's overwhelming power and his grandiose vision. The castle ruins have been designated a special national historic site.

The entirety of the small hill of Mt. Azuchi is the castle grounds, and by climbing the entire mountain, you can relive the scenery that Nobunaga would have seen at the time. The main road and stone steps have been maintained, and the remains of the residences of Nobunaga's vassals and Buddhist facilities are scattered around. In particular, the view from the tenshudai ruins is wonderful, with a panoramic view of Lake Biwa and the Omihachiman plains, and you can really feel the importance of this castle as a base for Nobunaga to unify the country.

It has also been selected as one of Japan's 100 Great Castles.

The nearby "Azuchi Castle Tower Nobunaga's House" has a full-scale reconstruction of the fifth and sixth floors of the castle tower.