MOUNT ASO: World's largest caldera! Circumference = 130 km (80 mi). Basically this is a series of 5 volcanic cones of which Mount Nakadake is still active. Hot springs abound in this area & a cable car runs to the top of Mt. Nakadake. Well, unfortunately, the cable car was not functioning the day we were there. So, I didn't get to see the fuming crater! But, may be it's a good excuse to come back? ;-)
Photo Credit: Postcard.