Relic Passage

Relic Passage (Japanese:  Ancient Passage) is a cave-like location in south Unova introduced in. It connects Driftveil City with Castelia City via the Pokémon World Tournament and Castelia Sewers, and is also connected to Relic Castle.

In the Pokémon Adventures manga
Relic Passage appeared in Colress Machine, where traveled through it after apprehending Bronius and Ryoku in the Castelia Sewers, following a stream of unusually cold air coming out of the cave. He eventually exited the tunnel near the Pokémon World Tournament construction site.

In other languages
Alter Fluchtweg Pasadizo Ancestral Chemin Enfoui Antico Sentiero こだいのぬけみち 古代小径