Ludwig's Thump Castle Hotel
From the Super Mario Wiki
Ludwig's Thump Hotel was a hotel found in Hotel Mario, owned by Ludwig Von Koopa. It was a horror themed castle. Enemies found in there, were Dry Bones, Boo Buddies, Big Boos and Swoopers. There are also vanishing doors to be found in the hotel, though if Mario finds Ghost Cologne, he will be able to stop them from vanishing.