I've visited that one. As a someone who grew up during the Cold War, the idea that we've got these once super-secret military aircraft just sitting where any old tourist can walk up and take picture from a few feet away always generates some cognitive dissonance.
In Palmdale California, at the corner of 25th St E & E Palmdale Ave [1], there's what is essentially a parking lot with a chain link fence around it. Sitting there are a SR-71, a A-12, a D-21 (supersonic recon drone originally launched from A-12 variant), and a U-2. You can just sit there and take all the pictures you want.
When I was in Boy Scouts we had a camping trip to SAC. A snow storm forced us to relocate inside and the Air Force came up with the museum as our temporary sleeping area. I got to sleep about 20 feet away from that SR-71. I will never forget how cool that was.
