Seven small lagoons sit in a line in the salt crust on the western side of the Salar de Atacama, invisible until you are almost standing over them — the ground is flat, white and blank, and then it drops away into a turquoise pool. The water is brine, denser than the sea, and in the one pool where swimming is permitted you float high enough to read a book.
Only the fourth lagoon is open for bathing, and the rules are strict: no sun cream, no insect repellent, no cosmetics of any kind before you go in, because the enclosed pools have no outflow and whatever goes in stays. There are freshwater showers on site to rinse off with afterwards, which you will want — the brine dries to a white crust on your skin within minutes.
It is about an hour from San Pedro on dirt road and access is managed by the local community, with an entrance fee and a cap on numbers. Sunset trips are the popular ones. It is quieter than Laguna Cejar and, for floating, better.