From Bulbapedia, the community-driven Pokémon encyclopedia.
Pastoria City (Japanese: ノモセシティ Nomose City) is a city in the region of Sinnoh. It also the home of the Move Relearner, and the Sinnoh region's Safari Zone. It is a city on the edge of a giant swamp, known as the Great Marsh. The marsh was once part of the sea, which drained away over time leaving the marshland. There are rare Pokémon only found in the swamps. The Great Marsh keeps the weather cool in the summertime, making it an ideal town for Water Pokémon. Croagunk is one of the rare Pokémon that can only be found in the swamp, so it is the city's official mascot.
The city's name may come from the word pastor, after the Gym Leader, Crasher Wake. Wake is possibly designed after Fray Tormenta, a famous lucha libre who was also a priest.
Pastoria City is also a home of Move Relearner's house.