Onioshidashi is the site of a catastrophic eruption of Mt. Asama in 1783. The lava flow, which was 2 km wide and 5 km long at the eruption, solidified into a carpet of jagged rocks. The site was named Onioshidashi (Demon’s Outburst) because the eruption was so violent that people at that time felt as if the demon was running amuck at the crater and pushing down lava rocks. Being called one of the bizarrest landscapes in the world, this lava field is nothing but the prodigious works of nature.

The area is now arranged into two parks; Onioshidashien and Asamaen (Asama Volcanic Museum). In Asamaen Park run by Naganohara Town, the 2,500 m natural trail is arranged for visitors to experience the power of Onioshidashi lava flow and the life force of flora and fauna inhabiting in this desolate land.