Akagi Shrine is considered to be the origin of Nagareyama. It is said that part of Mt. Akagi in present-day Gunma Prefecture broke off during a flood, and flowed down the Edogawa River, where it landed in the area that became known as Nagareyama (which directly translates to “flowing mountain”).

A massive shimenawa rope is adorned at the entrance of the shrine, spanning about 6.5 meters long, and weighing around 500 kg. It is a sacred rice straw rope that symbolizes purity. Every year on the second Sunday of October, you can watch the shimenawa rope being weaved together, and join a festival that is held here on the following weekend (the third weekend of October).