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Ryusendo Cave: Underground Lake of Iwate
Deep inside the mountain, the cave opens into a lake. The water is so clear that the measu…
Deep inside the mountain, the cave opens into a lake. The water is so clear that the measured visibility exceeds ninety-eight meters — among the highest recorded for any body of water anywhere. Ryusendo Cave in the Iwate mountains is one of Japan's three great limestone caves, and the least visited of the three, because Iwaizumi Town is not on the way to anywhere.
The transparency of the lake produces a color that has no equivalent in ordinary experience — a deep, still blue that intensifies as the light penetrates downward and the bottom recedes beyond sight. The limestone formations that frame it are secondary to this blue. Everything is secondary to this blue.
Iwaizumi is a small town in the Northern Sanriku highlands, not well connected by public transport. Most visitors to Iwate go to Hiraizumi or Morioka. The people who come to Ryusendo come specifically for it, which means they come prepared to spend time with it. This is the correct approach. The cave rewards patience. The lake, seen for long enough, begins to seem less like a geological feature and more like a decision the earth made about what kind of beauty it wanted to keep to itself.
The water here comes from underground. In Iwaizumi, the municipal supply draws directly from Ryusendo, a cave system that reaches deep into the limestone of the Kitakami mountains — so the tap water and the bottled mineral water sold at roadside shops are, in effect, the same source. That fact alone says something about the scale of what lies beneath this town.
The surface is shaped by cattle and cold. Shorthorn breeds arrived in the late nineteenth century, and the Japanese Shorthorn — Nihon Tankakushu — became the foundation of a livestock culture that still defines the valley economy. Iwaizumi yogurt is made here, thick and slightly sour, the kind that travels poorly and is best eaten close to where it was made. Matsutake come down from the surrounding Kitakami ridgelines in autumn. The mountains — Aokamatsuba, Ankamori — are not decorative; they press in on the settlements and determine what grows and what doesn't.
To the east, the land opens onto the Sanriku coast at Ohmoto, where the Rias line runs and the fishing harbor faces the Pacific. The cave of Ankado, a natural monument of extraordinary lateral extent, sits inland, largely unvisited on a given weekday. Between the limestone caverns, the pastoral valleys, and the coastline at Ohmoto, Iwaizumi holds three entirely different geographies within a single, sparsely populated municipality — each one quiet enough that you can hear the water moving beneath the rock.
Stay in Iwaizumi, Iwate
What converges here
- Anka-do Cave
- Iwaizumi Yūkutsu Cave and Bats
- Sanriku Fukko
- Mount Aomatsuba
- Mount Akka
- Mount Misugo
- Iwaizumi-Omoto
- Omoto Fishing Port
- Moshi Fishing Port
- Sukudo Fishing Port