The Nake-dake caldera is reason enough to visit Mt. Aso National Park. Inside the crater, a churning ash-gray lake bubbles and spits scalding, reeking steam. Naka-dake's rim is a 30-minute walk from the bottom of the Aso Nishi Cable Car at Asosan-jo; the cable car takes you up in four minutes. You can skirt around some of the lip, but the northern reaches have been out of bounds since 1997, when toxic fumes seeped out and killed two tourists. If rumbling turns to shaking, and steam and smoke turn to sizable ash fall, know where the bunkerlike shelters are located. These were built after a dozen people perished in a sudden eruption some 50 years ago.
Aso-san Cable Car, 808–5 Kurokawa, Aso, 869-2225, Japan