It is a very cool book. My daughter likes to sit on the couch with me and flip to random pages and find out about those places. We've been doing a couple items from the book every week for a few months now.
Atlas Obscura also hosts an "Atlas Obscura" day every year with events at various locations around the world. They are always looking for suggestions of places to host and every year I send in a request for the salt mines deep under Detroit. Sadly, they have not yet offered that. I'm sure it's the company that owns the mines that doesn't want the sort of security and insurance liability that comes with letting a group of tourists into their operation a few thousand feet below the surface of a major city.