The Onbashi Bridge is located in Taishakukyo Gorge, which covers the total length of 20 km on the border of Shobara City and Jinsekikogen-cho in the northeastern Horoshima Prefecture. The Onbashi Bridge　is a designated national Natural Monument and presumably one of the world’s 3 largest natural bridges. It is 90 m across, 19 m thick and 40 m tall. People call this huge natural bridge “Kami-no-hashi (the bridge for the god).”
When the Taishaku River eroded and crated the gorge, it also flowed into the underground and formed an underground river. In time, the river bed above ground fell in and the remaining part of the huge rock formed an arch bridge. It was used as a pedestrian bridge in the old times. It is a wonder of nature that was formed in an overwhelming period of time.