South Lipez, Uyuni and Atacama desert. Those places located North of Chile and South of Bolivia are part of the most popular and easy to access places in the Andean highlands. They are spectacular sites where you get totally disconnected from the rest fo the Planet. Sometimes it even feel that you are on Mars or some other place far from our universe. A “must-see” in life.
I would recommend doing the 4days trail from Tupiza to Uyuni for two reasons. First, most tourists do a 3days loop, from & back to Uyuni, with dozens of loaded 4×4 getting out at the same time and following the same road, which makes the sites very crowded. Starting from Tupiza, the traffic is way lighter and it should allow you to get some peace on the sites, with fewer people present. I personally appreciate it as it leaves you more pace and quiet to enjoy the magical surroundings. The second reason, is that you’ll do a big part of the South Lipez desert between Tupiza and Uyuni, which is a bit different than Uyuni but as stunning. Also, try to make sure with the tour company that you will watch the sunrise from the “Isla de los Pescadores”, truly spectacular!
About the Atacama desert and San Pedro de Atacama. It’s beautiful and a bit different than Uyuni, but be aware that the prices in town are higher that they should, and most tour and excursion are quite away from town, and a bit pricy (from a backoacker point of view.) Still, it has a lot of marvelous wonders to see all around.