Home of the Biosphere 2. Yes, it is still there, and visitable. A highly biospherical experience. Machinery that keeps it running is impressive. The habitat sections reminded me of a zoo aviary, but without the birds.
Not only does it have a song, it has 1) the most fabulous limestone cave you've never heard of, 2) a pretty impressive used book store - medium sized and neatly groomed, rather than large and shaggy. Both are some distance out of town; this is less usual for bookstores. This one, consequent on its location in a ranch house, has not only (inside) a store dog but also (outside) store donkeys.
Men in 19c dude outfits prowl the streets, looking for tourists to accost with pitches for re-enactment shows of one shoot-out or another. Ouside of town, a roadside farm stand sells fried peanuts, with a bowl for sampling. Eat them shell and all, it says. My advice after trying it: don't.
You might think a restaurant with a sign - in English, just about the only sign I saw in English that wasn't on a pharmacy or dentist's - at the exit to the pedestrian customs walk-through, giving detailed instructions on how to walk there, would be a horrible tourist trap. I trusted the guidebooks and they were right, it was good. The menu was dominated by shrimp dishes, which I felt a bit unreal for an authentic Sonoran interior desert experience, so I had the chicken mole.