I once had a 9 hour overnight layover in Denver Airport. It’s a cool weird airport to get stuck in. I didn’t bother to walk out to Blucifer. The infamous mural was still up, and it has a lot of detail that you can see a lot better up close in person, but the most memorable parts of that layover for me were the luggage gargoyles (which are fairly small, cute things) and watching the sun rise over the mountains from one of the terminals. Still, I wouldn’t do it again, a 9 hour layover sucks.