Wreckage of Starship SN8 at the Launch Site.
SpaceX Space Launch Site
Brownsville, Texas
This is where SpaceX builds and launches its big Mars "Starship" rockets. Although it occupies an out-of-the-way spit of land, it's far more easily viewed by the casual roadside public than any tour-only NASA facility. The launch (and later wreckage) of Starship prototype SN8 in December 2020 was a highlight, but the retro-style stainless steel rockets are being built upright and outdoors -- at least for now -- so there's usually something to see. There are no tour busses and no pre-visit reservations; you just park your car by the roadside and gawk.
Starship prototype SN9.
Get here quick before Elon Musk buys all the nearby land and blocks the view.