Boo Woods

Boo Woods is a location first featured in Luigi's Mansion. Boo Woods is extremely large and full of many dead trees; E. Gadd's lab is found here along with the mansion Luigi “won”. Boo Woods also appears in Mario Kart DS and Mario Kart 7; in these games it has a large swamp and some of the trees can move around. As the name implies, Boos haunt this area along with the leader of this area, King Boo.

Background
Boo Woods is first named when Elvin Gadd of the past mentions it in Mario & Luigi: Partners in Time. After his lab is destroyed by the volcano of Thwomp Volcano, he says he's got "a hankering to do some paranormal research" and that he plans to move to "an affordable lab at the edge of Boo Woods".

Luigi's Mansion
Prior the events of Luigi's Mansion, Mario goes to Boo Woods to go to a mansion that Luigi owns, waiting for his brother to meet him there. However, he goes missing. In the beginning of the game, Luigi goes to Boo Woods to find his mansion he won in a contest he did not enter. In the game, Boo Woods appears more like a background than an actual location. Luigi can go outside to the courtyards of the mansion, where Boo Woods is seen. The woods can also be seen in the balcony of the mansion.

Mario Super Sluggers
In Mario Super Sluggers, Luigi's stadium is set within Boo Woods, located in front of the mansion. Dead trees surround the ballpark, and the outfield contains gravestones and Ghosts which serve as obstacles to fielders.

Mario Kart series
The Boo Woods make appearances in Mario Kart DS, Mario Kart 7, and Mario Kart Tour in the Luigi's Mansion course. Outside the mansion is Boo Woods, which has a graveyard surrounding the mansion and beyond it, a swamp of mud with Walking Trees that act as obstacles.