From Bulbapedia, the community-driven Pokémon encyclopedia.
Ogi City (Japanese: オギシティ Ogi City) is an anime-exclusive large port city at the northern end of Yellow Rock Isle, one of the Whirl Islands in the Johto region. A ferry runs once a day between Ogi City and Red Rock Isle. This is also where Ash and his friends ran into Luka, who offered to give them a ride in her boat after they missed the ferry. In the oceans nearby, there is an old sunken ship which once belonged to Luka's grandfather.
Pokémon seen around Ogi City