After a major volcanic eruption, the magma chamber empties, collapsing into a cauldera, and there are generally two results. One is that the overlying stratum is so dense that subsequent magma movement is pushed to the side, as is the case with Sakurajima. The other is that the main magma channel remains permeable, and new peaks form within the cauldera, as is the case with Aso.
The Aso cauldera has five peaks: Takadake (高岳, 1592 meters), Nakadake (中岳, 1506 meters), Nekodake (根子岳, 1433 meters), Eboshidake (烏帽子岳, 1337 meters), and Kishimadake (杵島岳, 1326 meters). Now is foliage season. Drives and hiking paths ranging from easy to difficult are available. Kumanichi has a photo of Nekodake, a particularly attractive peak, coated in autumn leaves and bathed in fog. - William
