* Click a site name to more information.
The Horomankyo Gorge, which is made up of peridotites, stretches approximately 8 km to the east of Mt. Apoi where unspoiled mixed coniferous and broad-leaved forests extend along the mountainside. In particular, the predominant spread of Kitagoyo (P. parviflora var. pentaphylla) trees here at the northern limit of their habitat creates unique scenery that led to the area's designation as a Natural Monument of Japan in 1943. Locally known as a favorable late-October autumn foliage spot. The area is also home to hydroelectric power facilities that paved the way for the development of electricity sources in the Hidaka region in the early years of the Showa period (1926 - 1989), thus creating an air of industrial heritage. Although the forest road here is narrow and unpaved, the presence of evacuation spaces at key points allows vehicular passage.
The Horomankyo Gorge, which is located within the 10-km2 area of the Horoman peridotite complex, provides insights into the world of the earth's deep mantle. The area is dotted with sites that allow researchers to observe various types of peridotite.