From Bulbapedia, the community-driven Pokémon encyclopedia.
Mulberry City (Japanese: カジノキシティ Kajinoki City) is an anime-only location in Kanto. It is located between Tohjo Falls and Pewter City. In All That Glitters is not Golden!, May and the gang learned that there will be a Pokémon Contest there.
Mulberry City Contest Hall
The Contest started in New Plot, Odd Lot!. It was the last Contest before the start of the Kanto Grand Festival, so many of the Coordinators there were fighting for their fifth Ribbon, including May. Harley, due to having five Ribbons already, decides to help Team Rocket defeat May by lending his Banette to Jessie, who was entered as Jessebella. The two battle in the final round in the next episode. Meanwhile, James and Meowth trap Ash and his group in the box, but are freed by Drew and his Flygon. At the end of the competition, May defeats Jessebella and earns her fifth Ribbon.
Pokémon seen in Mulberry City