Ito-jo Castle was a yamajiro (a castle built on a mountain to take advantage of the mountain's topography) which had been constructed on the west hillside halfway up Mt. Takasu on the boundary between Fukuoka City and Maebaru City, Fukuoka Prefecture, in the Nara period of the eighth century.
怡土城（いとじょう）とは、8世紀奈良時代、福岡県福岡市と前原市との境にある高祖山の山腹西斜面に築かれた山城のこと。