We are having one of the bathtubs replaced. When the guy removed the old bathtub and a part of the dry wall behind it, he discovered a large empty enclosure behind the wall. I got excited, grabbed a flashlight and peered inside, hoping for Akhenaten's mummy or Thomas Say's lost notebooks or a portal to another universe or at least a bag of doubloons for crying out loud. But, alas, there was just dust.
Now we are trying to decide what to do with all that extra space we are suddenly endowed with. A closet of some sort is being planned.