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.

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