Brick shower?

There's a lot of brick in this house.  

Including, but not limited to, the downstairs bathroom:

Brick shower.  The third wall is also brick; the door is glass.

Above the shower head, there's this weird soffit thing.

It doesn't have any vents for heating or cooling.
It doesn't connect to anything on either end that has vents.
There's no stairs or anything above it.
There's nothing on the other side of the wall (where the outside is).

The contractor is going to excavate.  If there's nothing in there, he'll move the showerhead up to a more adult height.  If there's something important in there (but what could it be?), he'll cover it up again.

(The rest of the bathroom is also brick, but you only get pictures of the shower.)