Mt Iwasuge

Mt Iwasuge (Japanese: 岩菅山) is a nihyakumeizan* that rises quietly on the northern edge of Shiga Kōgen, a highland plateau in Nagano known for its volcanic terrain, deep forests and interconnected alpine wetlands. Iwasuge is a mountain shaped by ancient volcanic uplift, softened by centuries of erosion and surrounded by one of Japan’s most atmospheric high‑elevation landscapes. The area experiences massive snowfall and is a major centre for snow sports.

​

The topography of Iwasuge reflects Shiga Kōgen’s volcanic origins. The mountain is built of old lava flows and weathered rock, with long, rounded ridges and steep forested slopes that rise above a patchwork of marshes, ponds and ski valleys. The summit ridge is surprisingly open, offering wide views toward Mt Yokote (横手山), the Kusatsu–Shirane massif (草津白根山) and the distant North Alps. Shiga Kōgen is part of the Joshin’etsu Kōgen National Park, a region celebrated for its biodiversity and cool alpine climate. The mountain stands at the edge of this highland world, offering a quieter, more remote alternative to the busier peaks around Yokote and the Shibu pass. If one mountain is not enough, it's possible to hike along the ridge line for 45 minutes to the slightly higher Mt Ura-Iwasuge (裏岩菅山).

​

The hiking course typically begins either near the Shiga Kōgen ski areas or from the forest road to the north. I chose the latter, following a well‑marked trail that climbed steadily through mixed forest. The ascent is moderate but continuous, passing through dense forest before gaining the upper ridge. The views across the valley to the surrounding volcanic peaks are apparently spectacular, but unfortunately not when I went there. 

​

* 200 famous mountains of Japan

​

(All information here is based on personal observations and experiences. Check official sources before planning or starting any hikes.)