Yagi-jo Castle ruins is a National historical heritage registered in 1997. It is the remains succeeded for 400 years by the Yagi clan through Kamakura to Sengoku-Toyotomi era. The foot of the remains is organized with Goten-yasiki from Kamakura era, Yagi-dojo from the Northern and Southern Courts, and Yagi-jo Castle ruins which has a high stone wall built in Toyotomi era. Yagi-jo Castle ruins, especially, has the main building on 325 above the sea, 300-meter castle fort, and the stone wall is 100-meter wide.