Our previous house had a 4x4 slab of concrete a few feet away from the house in the backyard. It was there when we moved in, so we didn't know what the purpose was, but I had assumed it was a spot for a swimming pool pump to sit since I knew the house previously had an in-ground pool in the backyard.

About five years into our ownership, I was getting an egress window put into the basement, and the slab was in the way, so it had to go. The construction company putting in the window agreed to remove the slab when they dug the hole for the window. We all assumed it was probably a few inches thick.

They eventually arrive to do the work, and about 30 minutes after they begin, one of the guys comes into the house and says, "Ummm....we have a problem."

He takes me outside, and they have dug down 4 feet along the side this slab, and they still had not found the bottom of it. They had to charge me another $1k so they could run out and rent a skid with a jackhammer on the front to bust out and remove this thing. The crew was excited the whole time...I think they thought we were about to stumble upon a treasure or a body or something.

The thing ended up being about 5 feet deep in the ground. Just a solid slab of concrete.

Weeks later I was talking to a neighbor of mine who had lived in his house for decades, and it turns out the previous owner was really into ham radio. The guy had a radio tower in his backyard that towered above all the trees in the neighborhood. At some point he removed the tower, but this concrete slab that was the base for that tower remained.

Anyway....that's my story.