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.
It's a weird spot for an electrical outlet to, so I imagine whatever use it it for involves equipment or a device of some kind.
If the room the window leads to like a living room / sitting room? Could it be support for a projector of some kind for watching movies?
Nope, in fact to the left of the bedroom door is a washer/dryer and this perplexing little closet:
Laundry chute maybe?
Photo development lab with ventilation system and outside "don't open door" light?
Maybe? That's not a horrible explanation
Doesn't explain the mirror. Could have been they were keeping someone kidnapped there.