The mountainside of the Acanthian volcano is split into 5 regions or valleys, separated by 5 ridges. These valleys were formed naturally by lava flows during past eruptions. They are the north valley, the west valley, the south valley, the north-east valley, and the south-east valley. The ridges are the north-west ridge, the north-east ridge, the south-east ridge, the south-west ridge, and the east ridge. The ruins of Nomen are in the base of the northern valley, and the currently-running outpost town of Novale occupies the base of the western valley.
Except for the rim of the caldera, the mountainside used to be covered in trees. Now, the NE and SE valleys are completely bare, along with some of the N valley. The outpost towns of Nomen and Novale sit in the N and W valleys, respectively.
The Acanthians have put 1 stone watch tower on each of the ridges except the east ridge. The east ridge has been flattened on the top to build the main road in and out of Caldera City. The Calderan entrace into the tunnel on this ridge is flanked by 2 watch towers.