It's possible you are thinking of a different location or a different game. Could you please clarify what you're looking for?
For example, are you thinking of:
* The Ancient Tomb in Pokémon Diamond/Pearl/Platinum? This is a location where you need to solve puzzles to access the tomb and defeat the legendary Pokémon, Giratina.
* The Ruins of Alph in Pokémon Ruby/Sapphire/Emerald? These are a series of ancient ruins you can explore to find hidden items and Pokémon.
Please let me know what you're thinking of, and I can help you out!