Minecraft wiki entry for Woodland_Mansion, associated text: Although their exact structure varies, all woodland mansions have some things in common: they all have three floors with a variety of rooms, and generate a cobblestone foundation underneath the entire structure if there are any gaps between the bottom of the mansion and the ground. The top floor is about half the size of the lower floors, but the size of each top floor is pretty random for each mansion, depending on how many rooms are going to be generated on the top floor. Each mansion includes a large foyer that leads to the corridors connecting the rooms, a giant staircase also generates there, which leads up to the second floor. The foyer is dark and many hostile mobs spawn under the staircase.