You’re going to have to give some clues as to what we are looking at here. At first glance it looks like a flight of mini-stairs?

Landing?

Ledge

Ah!! It helps a bit if you turn the picture sideways . . .

I’d call it a ledge that doesn’t pass code because there’s no railing to protect someone standing on it.

Dust collector?

An accident waiting to happen?

Cat perch.

I agree that it looks like a non code compliant ledge. It needs a railing, or more. Looks like a hard and dangerous fall waiting to happen. Even with a railing it would still be treacherous for young children who are fond of climbing on things. Even the cat could take a nasty fall from that.

It also looks pretty dark and uninviting and slightly sinister. Maybe it is that dark descending staircase and that potential fall into oblivion that adds a sinister touch to it along with all that dark wood.

What is it called?.....a potentially life threatening accident waiting to happen and a very hefty lawsuit.