From Bulbapedia, the community-driven Pokémon encyclopedia.
The Oldale Ruins (Japanese: コトキ遺跡 Kotoki Ruins) are an anime-exclusive group of ruins near Oldale Town in Hoenn that appear in the episode A Ruin with a View.
These ruins are being studied by archaeologist Professor Alden who had read that there is a stone chamber within the ruins that legend states is a "bridge or portal between our world and the ancient Pokémon world". Because of its strange construction it crumbles whenever anyone attempts to enter it, however the stone tablet that Professor Alden possesses tells of four keys that can allow entrance into the stone chamber without it crumbling.
During A Ruin with a View Team Magma grunts supply Prof. Alden with the "four keys" which turn out to be four spheres. They then force him to apply the keys to the chamber door in the correct order so as to search the stone chamber. The first room of the chamber is empty with carvings relating to the ancient world on its walls, while a second secret staircase leads down to an underground lake which contains multiple Relicanth.
In other media
The Oldale Ruins are based on the Ancient Tomb and the other ruins where the Legendary titans may be captured. The stone chamber in the middle of the Oldale Ruins may be based on the Sealed Chamber that unlocks the Regi's tombs in the games.
In the Pokémon Adventures manga the instructions in the Sealed Chamber are on a damaged stone tablet, much like in the anime.
- The stone table from which Professor Alden learns how to access the stone chamber is very similar to the stone tablet that gave information about the legend of Pokémopolis. Coincidentally that episode aired exactly four years previous.
- The sealed door that led to the underground lake is very similar to the door that leads to the King of Pokélantis' tomb, in an episode that would air almost four years later.
The recurring stone tablet