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Joshin’etsukogen NP, Nagano
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A wooden torii beside Chigoike stands about 3 m high, yet coins are wedged into its top beam. The twist: winter snow rises high enough for snowshoers and backcountry skiers to reach it.
Yamanouchi Town’s 2025 cultural-heritage guide dates the volcanic activity that formed Chigoike’s hollow to about 600,000–700,000 years ago—far older than many Shiga Kogen ponds, formed around 50,000–100,000 years ago.
No river flows into or out of Chigoike: it is fed by rain and melting snow. An impermeable volcanic-ash layer beneath the pond helps hold that water high on Yakebitaiyama’s summit.
Sundews cluster along Chigoike’s edge. In the acidic, nutrient-poor conditions of a high moor, these small carnivorous plants trap insects to make up for nutrients scarce in the soil.
The vegetation shifts dramatically around Chigoike: low, 1–2 m dwarf pines grow near the wetland, while the nearby forest includes Maries’ fir and hemlock trees over 20 m tall.
The protected feature is Chigoike Marsh, about 5.6 hectares in area—not only the pond at its center. Yamanouchi Town designated the wetland a natural monument on October 30, 1976.
Chigoike’s seasonal show includes skunk cabbage seen around the summit in May and cotton-grass with its soft, white tufts; a park ranger reported the cotton-grass at its peak on June 25 in 2015.
