The Aso caldera is one of the largest volcanic calderas in the world, located in Kumamoto Prefecture, Japan. It was formed by multiple volcanic eruptions over the past 300,000 years, creating a vast depression that measures about 25 kilometers in diameter. The caldera contains several active volcanoes, including Mount Aso, which is known for its frequent eruptions and a large crater. Inside the Aso caldera, there are fertile plains and a variety of ecosystems, making it a rich agricultural area. The region is also popular for its hot springs, known as onsen, attracting tourists who come to enjoy the natural beauty and geothermal activity.