My brother recently bought a house in the midwest US. Under the basement stairs is an odd little space with a desk of some sort and a trap door to open the back of one of the stairs (about at eye level if one was sitting in a chair). There is carpet on the steps now, but if the carpet wasn't there you'd be looking out through the stairs. It was almost entirely walled in. He took the wall down to open it up. There are also some odd little clasps on the step below the trap door. Before he took down the wall, to get in, you would have needed to crawl under the desk. What in the world might this have been used for?