"Shibuya river" is a river that flows in the Shibuya station southwest.
Perhaps, this river's source is Tamamo-pond of Shinjuku Imperial Garden (N 35" 41.115 E 139" 42.832).
However, from the source in front of Shibuya station is a culvert, and the flow of the river cannot be seen.
Cache is setup near the Shibuya river appears the ground.