Last year I visited the Grants Mining Museum in New Mexico. I took the self-guided tour of the mine. I thought the elevator ride wasn't very long, but didn't think too much about it. I wandered down the route and was disappointed that the whole mine was grouted. I figured it must have been due to radon, or maybe they just didn't want to risk rockfall on the tourists. Do you see where this is going? When I returned up to the museum, I asked. They said, "No, it's not a real mine. We just made our basement up to look like a mine."