Its current appearance is of a floating black platform with green lines high in the sky, and is surrounded by multiple explosive mines. In Super Mario 64, it serves as the arena for the final battle. In some videos, it serves as the lair of SMG3.
Bowser's First Lair
During the earlier bloopers, Bowser had a different home. It was a blue rocky platform located in the center of Dark Land, similarly surrounded by multiple explosive mines. This arena is actually the arena for the first Bowser boss battle in Super Mario 64.
Bowser's Lair has appeared many times throughout the series. It usually appears when the characters have to meet up with Bowser, although it tends to also appear in other scenes. It frequently appears when Bowser or SMG3 are plotting an evil plan.