Dream World (Pokémon)

The Dream World was a realm of dreams created by the Unown. It was the site of a major tournament of Pokémon trainers from different worlds throughout the Pokémon Multiverse, including Gash Ketchum. It's a single Dream World extending throughout all the Pokémon worlds. For this reason it's possible this is the same Dream World seen in the PCG Multiverse, but this hasn't been confirmed. (Pokémon Tales Prose: "Crisis in the Dream World")