From Bulbapedia, the community-driven Pokémon encyclopedia.
Volley Town (Japanese: バレータウン Valley Town) is an anime-only location in Hoenn. It was featured in the episode Crazy as a Lunatone. It is located between Fortree City and Lilycove City. Volley Town appears to be based on a classic western town, complete with tumbleweeds. It is surrounded at all sides by high mountains and very steep cliffs. At the edge of the town there is a location called Camerupt Point.
When Ash, Brock, May and Max were on their way to Lilycove City for May's next Contest, they decided to take a rest at Volley Town, only to discover that the town was deserted. Even though the town looks old and uncivilised, it has a Pokémon Center. Ash and his friends went here and discovered that the town was not completely deserted: a Nurse Joy showed up, though she acted strange.
Later, it was discovered that the Nurse Joy's mind was actually controlled by a Lunatone that crash landed nearby from space.
Pokémon seen in Volley Town