The Julma-Ölkky canyon is is a several kilometres long fracture valley. The Julma-Ölkky canyon lake was formed in it. The lake is about three kilometres long and, at its narrowest, only ten metres wide, but it is about 50 metres deep. From the surface of the lake, the rock wall rises to the heights of 50 metres. After a narrow neck of land, the canyon fracture continues for one more kilometre, taking the shape of Lake Pikku-Ölkky and Ölkynlampi Pond.
There is a small rock painting in the southern part of Julma-Ölkky, depicting two people and a moose or reindeer. It is the northernmost rock painting found in Finland, and you can only see it from a boat, or from the lake ice in winter. There is a vault-like rock fracture, Pirunkirkko (Devil’s Church), in the middle part of the canyon lake, next to the hanging bridge. According to a legend, a wise man’s place of worship was located in the fracture and he cast spells there.
Julma-Ölkky is the uppermost lake in the Hyrynsalmi route, which belongs to the River Oulujoki watercourse. The waters flow, via Lake Kiantajärvi and Lake Oulujärvi, to the Bothnian Bay.