Patrick Nouhailler's pictures .

Villazón  is a town in southern  Bolivia , on the border with  Argentina . It sits directly across a river from  La Quiaca  in Argentina. The town is a busy trading hub, with large quantities of goods flowing north. It is also a heavily used transit hub for tourists passing into Bolivia. A train line connects Villazón with  Tupiza ,  Uyuni  and  Oruro . Two train services, the  Expreso del Sur  and slightly cheaper  Wara Wara del Sur , each run twice a week. Buses also connect to many destinations.

Salar de Uyuni Salar de Uyuni  (or  Salar de Tunupa ) is the world's largest  salt flat  at 10,582 square kilometers. It is located in the  Potosí  and  Oruro   departments  in southwest  Bolivia , near the crest of the  Andes , and is elevated 3,656 meters above mean sea level.  The Salar was formed as a result of transformations between several prehistoric lakes. It is covered by a few meters of salt crust, which has an extraordinary flatness with the average altitude variations within one meter over the entire area of the Salar. The crust serves as a source of salt and covers a pool of  brine , which is exceptionally rich in  lithium . It contains 50 to 70% of the world's lithium reserves,  which is in the process of being extracted. The large area, clear skies and exceptional surface flatness make the Salar an ideal object for calibrating the  altimeters  of the Earth observation satellites. ...