Smack in the middle of the Salar de Uyuni is the “island” of Incahuasi. It’s densely covered with cacti (and I rediscovered the hard way how much a cactus needle can hurt). It’s well worth the very short climb to the summit for the views.
There’s a small cultural museum on the island, and a tiny restaurant/snack bar. Also a cute resident llama, that I’m sure is regularly switched out for a younger one as it ages, that has a small money pouch around her neck for small picture-taking donations!