The Plains are a location on the Friend Area Map in Pokémon Mystery Dungeon: Red Rescue Team and Blue Rescue Team. They sit just north of Pokémon Square. There are (?) Friend Areas at this location, housing a maximum total of (?) Pokémon.
Sky Blue Plains
Sky Blue Plains is only available after the main story has been finished. It can be obtained by completing rescue missions that list "Friend Area" as their reward.
After this Friend Area is obtained, a story mission can be found on the mission board, allowing the player to go to the Howling Forest and rescue Smeargle.