This is the Viaduct "La Polvorilla," an engineering masterpiece on the already complex train to the clouds. At 4220 m, the viaduct is 224 m long and 63 m high, It curves and slopes at the same time and is located near the end of the 219 km route from Salta, through the Valle de Lerma, up to the puna, or high altitude plains.
The railroad was built in the 1920's for British railways, designed by an American engineeer, to provide access to the nitrate mines in Chile.and reaches 14,000 ft. Passengers must take care of the altitude, and a cup of coca tea will help.
The trip today is for sightseeing, and there are stops along the way for photographs, and one in San Antonio de los Cobres for refreshments and handicrafts shopping. San Antonio de los Cobres is a copper mining town, set in a dry, treeless area. Be careful of the sun.