Mama Plant’s house as the kitchen and dining room together, and the tax man was reluctant to believe that a home in that neighborhood had four rooms. 
Taxes here are based on property value. You could have a large house in a poorer neighborhood, and not have to pay the same amount as the people living on Nob Hill. Nor should you.
Awesome thread! Just to make sure I’ve got the layout right - you open the previously-sealed door, and there’s a pedestal and telephone, and directly above that is a hatch?
I keep checking back on this thread hoping for some pictures.
I still think that is was a laundry chute before the house became a duplex. 
But it is more fun to think of Al Capone’s hideout.
That is correct.
Did you ever ask the tenants in the flat above, what they have in that same space in their unit? Are they using that space? Is it sealed shut too? If you climb up the beanstalk, through that hatch above, will you be in their space? Will you be in an alternate universe? Will you be in a little twisty maze of passages, all alike?
So much yet to explore here! You have a little Winchester Mystery House in the making!
Department of Motor Automobiles?
And what ever you do, don’t take a shower. 
Probably painted over the holes.
Any busts of William Shakespeare with a swivel head?
Defense
Materiel Admin
or
Mapping Agency
Open it! Open it! Open it!
The mystery hatch in the ceiling? I’m not sure of the legality of cutting the lock.
Who’ll know?
Hmmm. The lock is in your rental space. Is it owned by your landlord? Does your landlord know you opened the painted over door? What will he/she say to what you’ve already done?
I would imagine the key is lost if you can’t find it in that room, so removing the lock just so you could put on a new one with a key you have would be legal. Opening to see where the hatch goes is probably legal - it’s a door you have access to from your space. If it’s locked on the other side as well, there you go.
Now things might get a tad uncomfortable if you open the hatch and surprise your upstairs neighbor doing the laundry or something.
Of course, you might be in violation by opening the closed off area and therefore have violated your lease or something. And that might open you to liability for cutting the lock/opening the hatch, since it is not in your designated space.
Consult your rental agreement before proceeding? Inquire of your landlord about the space? Ask your neighbor about their floorplan? Invite them in to show them your new pantry/closet/study cubicle?
Defense Mapping Agency, There were detailed maps of Military bases, including the Secret areas that are blacked out on most maps.
I rent a house to a guy, and if he opened a sealed up area, I’d be hacked off. If you uncover the end of a laundry chute or dumb waiter that goes into someone else living space, they will be hacked off as well. If my tenant asked what the hell it was, I would tell him.
If that does go into someone else house, I think you will be breaking and entering, at east breaking.
It can’t really go into someone’s house, unless they have a mysterious three foot deep divot in their floor. (Yes, I measured. Some of my closets lack ceilings, and there’s three feet between my ceiling and the upstairs floor.) My lease didn’t state anything about the sealed off door (or any “sealed” space), so I can’t be in violation until I start cutting off locks, which would probably be destruction of the property, at most.
That is odd.
Three foot mystery ceiling space … what could go wrong? Are there stains? Explore please.
The Fridge of Doom discovery, The Piggy in the Crawlspace treasure hunt and of course The Mysterious Electrical Wire and now this!
It’s the Punishment Room.
Don’t open it. You’ll regret it. Forever.
sobs