01 / Amasaki Castle Ruins (甘崎城跡)
From the shore to the seabed,38 stone walls, large and small, are confirmed.
The ruins of a naval sea castle on Furushiro Island (古城島) in the Hanaguri Strait (鼻栗瀬戸), near the east coast of Ōmishima, and a prefecturally designated historic site. The whole island is the castle site, thought to measure about 300 m east–west and 80 m north–south. The rocks hold many post holes thought to be mooring facilities.
- Stone walls: 38 in all, large and small, about 500 m in total (prefecture)
- Prefectural historic site (April 16, 1976)
- Lords named in records: Murakami Michiyasu, Imaoka Minbu, Murakami Yoshitsugu (prefecture)

