During the events of Super Mario RPG: Legend of the Seven Stars, Bowser's Keep is isolated on a mountain of red, jagged rocks. The keep rests on the largest rock, which, in fact, resembles Bowser himself. The castle can only be accessed by a long bridge that connects to the faraway Vista Hill. The halls of Bowser's Keep are lined with statues of Hammer Brothers and Bowser. The castle is originally guarded by Terrapin soldiers. Additionally, molten lava flows through the keep in several areas. Fortunately, several bridges allow access across the lava. Unfortunately, the bridges are wooden, and as such, will eventually collapse in a room filled with lava. In fact, one bridge breaks right after Mario walks across it. Later, this bridge is replaced with hovering Donut Blocks. The castle is also filled with ornate chandeliers. Mario and Bowser actually duel on the top of these chandeliers.
Bowser's Keep is also the Smithy Gang's base of operations in Mario's World. During the beginning of Smithy's invasion, the gigantic sword Exor crashes into the keep. Since Exor is the gateway to Smithy's dimension, the soldiers of the Smithy Gang have an easy time taking control of the castle. In fact, many of Bowser's soldiers defect or run away instead of fighting. Eventually, the Smithy Gang claims the castle as their own. Additionally, Exor destroys the bridge connecting Bowser's Keep to the outside world. As such, the castle can only be accessed by flying vehicles.
Before the fight against Magikoopa, there will be 6 doors to choose from, though only four doors are required. There are two action courses, two battle courses, and two puzzle courses.