What is above the closet? Things like plumbing and duct work can be hiding in these spaces (I'm assuming the closet is on the first floor and there is a room/space above it). Staircase landings, old hearths, etc have all been known to take up head room in these old houses.

And beware of "busting open" things in old houses. The amount of lead paint and asbestos filled material can be quite large. So long as they remain in tact (undisturbed by hammer and chisel) you are perfectly safe. As soon as you "bust into" something, you could make the safe "unsafe".

Congratulations on the new "old" home! They are beautiful. They take a certain approach to renovations that new homes do not require: testing everything before disturbing it.

Find the blue prints and see if you can work out what is there before you "bust it open". Pretend you are a detective working a case. Before you damage your property (these old buildings are like Pandora's box...sometimes it is better to leave them alone), try to puzzle it out before hand.

It was fairly common through WWII that closets would have low ceilings. People stored less, and applying wet plaster in a tiny closet while standing on a 8 foot ladder wasn't fun. 'Usually' there is nothing above, you should be able to check from the attic.