Northwest of Naruko town, this 100m-deep gorge is particularly spectacular in the fall when the leaves change colour. The trail leading to the gorge from town has been closed for repairs for some time, but should reopen in 2017. There's an alternative course though, which takes about an hour to loop around two bridges.
The latter trail can be reached from Nakayama-daira Onsen Station, which is a short bus trip from Naruko Onsen Station (¥180, five minutes), or an easy, well-signed walk. This path also intersects with a 10km stretch of the old foot highway, walked by the haiku poet Matsuo Bashō, which is now a hiking trail. Pick up maps and the latest trail info at the Tourist Information Center.