A spectacular roller coaster of a road crosses the mountains into Argentina, 185km east of Vicuña. At an ear-popping 4765m above sea level, it's one of the highest Andean passes between Chile and Argentina. It's also one of the best areas to see the frozen snow formations known as penitentes, so called because they resemble lines of monks garbed in tunics. There are also accessible glaciers on both the Chilean and Argentinean sides.
From Vicuña, Ruta 41 climbs along the Río Turbio to the Chilean customs and immigration post at Juntas del Toro. It continues south along the turquoise reservoir known as La Laguna before switchbacking steeply northeast to Agua Negra. The road leads to the hot-springs resort of Termas de Pismanta in Argentina, and to the provincial capital San Juan.