Moonlight Kingdom

Moonlight Kingdom is a rare anomalous area in Super Mario 64. It's an area similar to the original castle interior but with one painting on the left leading to a level called Misty Mountain with night themed wall textures, there are also stairs leading up to a star door and a large moon above the entrance. The appearance of this area will signify more anomalies afterward.

Documentation
There is only one video documenting Moonlight Kingdom, you can watch it here.