We might need a bit more information to help solve the mystery. How long have you had the closet? When did you notice the hole? What’s on the other side of the hole? What is the white stuff at the top of the hole? What is on the level below the closet? I’m thinking it could, possibly, be for a laundry chute?

I noticed the hole in my closet when I first bought the house, almost 3 years ago. It is up on the second floor. I looked inside of the hole with a flashlight. There is nothing there. My bedroom has walls made out of wood panel, so the brown you see in the photo is the inside of the wood panel from my bedroom wall. The white stuff in the hole is some type of plaster and is sitting on the wood inside the wall. The level below the closet is the hallway.

Hi we live in a 245-year-old home and when we bought our house we had the exact same closet dilemma in a 2nd floor bedroom closet. We found out that the previous owner was searching for another fireplace because the closet was on the other side of the central stack of the fireplace below. We decided to just close the hole since we have enough fireplaces. The mystery lives on.....

Depends on the age of the house somewhat...my '50s house has a of things inserted into closet walls like shoeracks. I think it's the one halfway down this article: https://retrorenovation.com/2011/07/17/7-odd-and-inventive-home-features-from-1954-including-a-fascinating-island-type-drainboard-sink/

In a '20s house I had a really nicely finished and trimmed door in a closet about that size that went to the plumbing shutoffs in the neighboring bath, but I guess that's not the case here!

ForI, thanks for that link! Very forward-thinking! The dust chute? Forerunner to our central-vac system with dust door! Package receiver for Amazon and Chewy! (I had a milk door, but I sealed the door on the inside and used the outside door for my little garden tools, just right for my rowhouse pocket garden.)

I think easy access like yours to the plumbing would be great.

My mom had one in her 1980’s house. Previous owner had a security system at one time and the control panel (or whatever it’s called) was in the closet.

I don't know, but I wouldn't worry about it. I'd simply cut out that insanely poor repair above the opening, do a standard drywall patch, paint it, and forget it.

I'd get a shoe rack :)

It looks like some kind of beaverboard-do you have an old house? Maybe they cut out a piece to patch somewhere else in the house.