Not actually my house, it was an AirBnB outside Seattle, but it's mysterious and I'm hoping someone here might know the function.
Inside the main closet in the master bedroom is a weird giant staircase leading to a square hole that looks into the area outside the bedroom. Here's the other side:
The inside of that cupboard beneath is just a small empty space, much smaller than the staircase, tiled at the bottom and possibly sized for an electric fireplace or something.
My friends and I could not figure out what it was supposed to be, and it's driving us a bit crazy.
Are we sure the floor inside the cupboard doesn't lift up? Could this be where the sump pump pit is for the house, and the weird stairstep closet is the compromise to use the otherwise unusable space?
Positive, it's tile and I checked. Maybe it's a staircase to a basement access that's been sealed? But that doesn't explain the window.