Onioshidashi Park, Karuizawa Overview
A field of black lava boulders left by Mount Asama's catastrophic eruption of 1783, with paths threading through it and a temple built in the middle. It looks like nowhere else in Japan. Two things to know: it is in Gunma rather than Karuizawa, about 40 minutes by car, and public transport out here is seasonal and thin, so this is a drive or a tour.
