Mount Aso
I don’t think that hot spring is good for baths.
Mount Aso (阿蘇山, Aso-san?) is the largest active volcano in Japan, and is among the largest in the world. It stands in Kumamoto Prefecture, on the island of Kyūshū. Its peak is 1592 m above sea level. Its caldera is 25 km across north to south and 18 km across east to west. The caldera has a circumference of around 120 km (75 miles), although sources vary on the exact distance.
The central cone group of Aso consists of five peaks: Mt. Neko, Mt. Taka, Mt. Naka, Mt. Eboshi, and Mt. Kishima. The highest point is the 1592 m of Mt. Taka. The crater of Mt. Naka, the west side of which is accessible by road, contains an active volcano which continuously emits smoke and has occasional eruptions.
The present Aso caldera formed as a result of four huge caldera eruptions occurring over a range of 90,000–300,000 years ago. The caldera, one of the largest in the world, contains the city of Aso as well as Aso Takamori-cho and South Aso-mura. The somma enclosing the caldera extends about 18 km east to west and about 25 km north to south. Viewpoints from the somma overlooking the caldera are perched upon lava formed before the volcanic activity which created the present caldera.
Ejecta from the huge caldera eruption 90,000 years ago covers more than 600 km³ and roughly equals the volume of Mt. Fuji; it is presumed that the pyroclastic flow plateau covered half of Kyūshū.
If you want to see a REAL volcano that is still active and may erupt at any day, this is the place to go. A little excitement and false adrenalin that your life is in danger from a near erupting volcano can be quite fun :)
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