Could you be thinking of:
* The Golden Room in Pokémon Mystery Dungeon: Red Rescue Team and Blue Rescue Team: This is a special room in the game that appears randomly in dungeons. It's golden and has a treasure chest in the middle, which always contains a rare item.
* The Golden Tower in Pokémon Mystery Dungeon: Explorers of Time, Explorers of Darkness, and Explorers of Sky: This is a special dungeon located in the Temporal Tower. It's where you fight the legendary Pokémon Dialga, Palkia, and Giratina.
* The Golden Tower in Pokémon Mystery Dungeon: Super Mystery Dungeon: This is a special dungeon that contains a treasure chest with a powerful item.
If you can provide more context, I can help you find the specific location you are looking for.