Black Room of Death
A black room of death is the name given to the area behind a loading zone door.Despite the name these rooms don't actually kill Mario. There are 6 BRoD in the game:
1. Behind the castle's enterance
2. Behind the basement door
3. Behind the door to the courtyard
4. Behind the door to the upstairs area of the castle
5. Behind the moat door
6. Behind the door in the Cool, Cool Mountain slide (slide side only)
See also
https://youtu.be/pZYHMY6tyeU -(Video off all BRoD)