There are 17 levels in total to clear in Luigi’s Mansion 3, including a Fitness center, located on 13F. While making your way through it, you’ll get locked inside the Training Room. You’ll need to find a gold key to get out, here’s where to find it.
13F Training Room Key Location
About midway through the 13F level in Luigi’s Mansion 3, you’ll find yourself in the Training Room. The door leading to the next room will lock here, and you’ll need to find the key. It is hidden in one of the exercise bikes. Specifically, you will need to use the vacuum on the middle exercise bike. This will give you the key needed to proceed.
Where to Use the Key
Once you have the key for the Training Room, you can use it to unlock the door into the Yoga room. This is where you’ll find access to the outside area, as well as the boss room (he’s pretty easy to beat!)