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The Roundhouse is an outdoor area of the Old Clockworks in Luigi's Mansion: Dark Moon. The first floor of the Roundhouse is accessed by taking north door on the first floor of the Warehouse or by taking the west door on the second floor of the Canyon Stairs. The second floor of the Roundhouse is accessed by taking the north door inside of the Clockmaker's Chambers. The Roundhouse is an abandoned minecart facility. The first floor features a turntable with a track that can be moved. A chain lowers the ramp so that access can be granted between both sides of the Roundhouse. A track is present on the left side, but is broken away from the turntable and unusable. There are crates and bricks littering the turntable. The flooring on the second floor is broken, leaving only thin metal bars that Luigi can walk across. On the first floor, the door to the right leads to the Canyon Stairs while the door on the south takes Luigi to the Warehouse. On the second floor, the door to the north and the west leads back to the Transportation Hall while the door on the south leads back to the Clockmaker's Chambers.
During Roundhouse Brawl, Luigi needs to make his way to the first floor of the Roundhouse where the Ancient Poltergeist has taken the minute hand. However, the way to the Poltergeist is blocked, so Luigi needs to go across the second floor of the Roundhouse. When Luigi finally reaches the part of the Roundhouse with the Ancient Poltergeist, Luigi has to battle him. During Play Catch, the Polterpup escapes to the Roundhouse after Luigi finds it in the Drafting Office. Before Luigi can capture the Polterpup, a Greenie chases it away. During Outlandish Interruption, the Roundhouse might be one of the rooms infested with ghosts, if so, Luigi will have to fight a single Poltergeist.
Starting from Roundhouse Brawl, after Luigi crosses the metal bars to reach the other side of the second floor of the Roundhouse, there is another set of metal bars going south. Taking this route takes Luigi to a Treasure Chest that contains a ruby.