From Bulbapedia, the community-driven Pokémon encyclopedia.

Frodomar City is the hometown of Ritchie. It is probably located in Kanto, and is only mentioned in the dub.

Anime- and Special-exclusive locations in Kanto

A.J.'s Gym | Cerise Island | Chrysanthemum Island | Camomile Island | Crimson City | Dark City | Fennel Valley | Frodomar City | Gaiva Dam | Gardenia Town | Grandpa Canyon Gringey City | Hidden Village | HopHopHop Town | The House of Imite | Kas Gym | Leaf Forest | Maiden's Peak | Mossgreen Village | Mulberry Town | Mt. Hideaway Neon Town | New Island | Pokémon Land | Pokémon Tech | Porta Vista | Potpourri Island | Rifure Village | Rota | Sayda Island | Scissor Street | Silver Town | Stone Town Sunny Town | Terracotta Town | Tree of Beginning | Wisteria Town | Yas Gym