Do you own or rent? If you own the home, call in a contractor to see if it is something for function so you know your options. If it's a rental, ask the landlord what it is. If it isn't functional, you can remove it or just put a rug over it for safety.

Looks like a cold air return. You wont feel air being sucked in ... though you may also want to consider cleaning it. We have one, but it's on the side of the room, so we have a love seat sitting over it (decently long legs, no skirt, so air can get under without a problem.

How in the middle of the room is this?

It might be an air return from an old convection furnace (no fan). BIG ducts, all gravity flow, hot air rises, cold air drops. Typical of old coal-fired furnaces. With no air in or out of it, it was probably taken out of service at a furnace replacement long ago. How to make it safe? Take it out and patch in the flooring? Put an area rug over it? Nice toes!

That's the grate for a floor furnace. Back in the day they were everywhere. Playing tag in the house, my cousin fell on one and burned a grate pattern on her butt and legs. If you can't remove it and feather in flooring, just cover it with an area rug. You might take a file and file down any rough spots where you've gotten hurt before you cover it up.

Are you sure it's disconnected from everything? Are you positive it's not the return air intake?

Call in a local flooring company and see if they can remove the grate, put down subfloor, and patch in matching flooring.I notice you have some very old floors. might be difficult to match. can you get them refinished? they could patch in something similar, refinish the old ones, and stain everything the same to match.

At the very least you could have a piece of plywood put down, make it level w/the other floor, and cover it w/a rug.

Or, have them lace in same type of flooring and get it refinished, or,, cover that until you can afford to get the whole thing redone.

If it's a little off, throw down some type of rug or runner

If all of that is too much trouble, just find a floor mat to cover the grate

90% sure it’s a floor furnace (or was). If youve had central Hvac installed these sometimes get left in place because it’s cheaper than actually patching the floor

@decoenthusiaste is right. We had one in my first childhood home. I have burn scars from it on the back of my hand. Mean big sister took my stuff and I ran after her and fell. Not that I'm still mad about it or anything. 😛

Sure looks like a floor furnace grate to me. Given the NOLA location, I suppose it could have been part of a ventilation system (primitive AC) to allow cool air to enter the house and hot air to exhaust somewhere near the top of the house. But most likely a furnace.

Yep I had one twice that size in a rental the first year's I taught in a small town. House was tiny and over 100 years old, rock wall basement. It was my ONLY heat source so I did not do anything that blocked the heat.