This dam was built in 1657 to control the stretch of the Shakujii River known as the Otonashi and to divert part of the flow into irrigation canals leading through fertile rice paddies. This stretch of the river is one of several place names in the Ōji area that were borrowed from the Kumano region to the west of Edo in the Kii Peninsula, in deference to the dedication of Ōji Gongen Shrine to the gods of Kumano. Ōji Gongen Shrine still stands on the bluff across the Otonashi River from Asukayama, or just to the right of the point where Hiroshige has placed us in this view.