Pastoria City is Far south of Sinnoh and is home to the The Great Marsh Safari area. Pastoria City collects a lot of rain due to it being the warmest area in Sinnoh's overall cold climate so its best not to get knee deep in marsh mud or that would be very problematic for you. The City's Gym Leader is a master of Water type pokemon and very tough compared to the others before so best watch out before you find youself facing tough briney deep pokemon.