Looming ominously over Karuizawa is 2568m Asama-yama (浅間山), Japan’s highest triple-cratered active volcano, which last erupted in 2004. The closest you can get to the crater is on its north side at Onioshidashien (鬼押出し園), 21km from Karuizawa. Onioshidashien was the scene of a cataclysmic eruption on August 5, 1783, when ashes from the blowout were said to have darkened the sky as far as Europe, and a 7km-wide lava flow swept away Kanbara village. When the lava cooled it solidified into an extraordinary landscape of black boulders and bizarre rock shapes, where alpine plants now sprout and across which twisting pathways have been laid. To see the scale of the place, head up to the observation floor in the gift shop and restaurant complex at the entrance. Most of the crowds head for the central temple, Kannon-dō, standing on a raised red platform amid the black rocks, but you can easily escape them by continuing past to the quieter area behind.