In the mid-thirteenth century, Emperor Go-Saga and his son Emperor Kameyama turned the area into an imperial villa which they called . The name "Kameyama", which literally means "turtle mountain", was selected due to the shape of Mt. Ogura, which lies to the west of Tenryū-ji—it is said to be similar to the shape of a turtle's shell. All Japanese temples constructed after the Nara period have a "sangō", a mountain name used as an honorary prefix. Tenryū-ji's "sangō", , was also selected due to the shape of Mt. Ogura.