Pipe House (Mario & Luigi: Superstar Saga)
From the Super Mario Wiki, the Mario encyclopedia
The house has three red Warp Pipes and one green one. The green pipe takes the Mario Bros. to locations they have visited. The two red pipes on the end warp the brothers between them, and the third red one houses Piper. By using these Pipes and talking to Piper, players can figure out their purposes in the game.