Akayako is a lake, located in northern Gunma prefecture and actually it is a dam called Aimata. Sarugakyo onsen (hot spring) is located along the lake and there are 16 hotels which attract clients from all over Japan.
The hotels and other hot spring facilities were originally located adjacent to Akaya river but abolished when the dam was created in 1952 but reopened in 1958 on the shore of Akayako. The name of the onsen was originally called Yushima onsen but renamed to Sarugakyo onsen in 1958.
Sarugakyo onsen and Akayako can be reached by bus from Jomokogen station of Joetsu Shinkansen or Gokan station of JR Joetsu line.