S P O T ／ SPOT-080

Kanayama Megaliths / Iwaya Iwakage Site (Japan's Stonehenge)

金山巨石群・岩屋岩蔭遺跡かなやまきょせきぐん・いわやいわかげいせき

In the wooded hills of Gero's Kanayama district, a scatter of enormous granite boulders has been arranged — or, the more cautious researchers say, naturally placed — in a configuration that appears to function as a Stone Age solar calendar. On the days of the autumnal-equinox-adjacent festival of frost (Sōkō, around October 23) and the late-winter festival of melting (Usui, around February 19), sunlight at a specific moment in the afternoon passes through a narrow gap between the megaliths and strikes a precise spot inside a cave-like structure called the Iwaya Iwakage. Below the rocks, excavation has yielded stone arrowheads and pottery from the Jōmon period some 8,000 years ago, alongside artifacts continuing into the Edo era. The site was designated a Prefectural Historic Site in 1973. Above the megaliths sits the small shrine Iwaya Iwa-jinja, which incorporates the Heian-era legend of the warrior Akugenta Yoshihira slaying a hihi monkey-monster here, layering Stone Age archaeology, prehistoric astronomy, medieval folklore, and active local Shinto into a single hillside. Local volunteer guides run interpretive tours and are by far the best way to grasp the site.