The Horoman River, originating from the Hidaka Mountains, flows into the Pacific Ocean. Approximately 8km of its middle and lower reaches is a natural gorge that continues along the east of the Apoi Massif (Pinneshiri ~ Mt. Apoi), and is called Horoman Gorge. It is a gorge formed by the same "peridotite" as Mt. Apoi, and perhaps because of that, the flow is uniformly blue-green, and together with the mountain slopes of the coniferous and broadleaf mixed forest, it creates a beautiful landscape. Especially, in autumn, the autumn leaves are beautiful, and it is a famous place known only to those who know.

Also, along the way, there is also a hydroelectric power plant that marks over 70 years of history, and it also has an aspect as industrial heritage. The paved road is from the river mouth up to 2km, and beyond that, it is a gravel road with a narrow width, but because many pull-out spaces are prepared on the roadside, passage is sufficiently possible even with a passenger car.