I embarked on a day trip from the city of Salta to Humahuaca, in the far north of Argentina (only about 150km from the Bolivian border), which follows the line of the Camino Inca, a major cultural route, along the spectacular valley of the Rio Grande. Enroute to Humahuaca, you can break up the dramatic (and long!) journey with visits to Purmamarca and Tilcara. The alluring, if not dusty, town of Purmamarca, is theatrically set beneath The Hill of the Seven Colours (Cerro de los Siete Colores), which is a sight that has to be seen to be believed. Even if geology is not ure thing, it's impossible to not be wowed by the spectacular colours of Purmamarca hill. The hill's unique layers of various colours were formed by sediment over 600 million years ago when the area was underwater...now it's over 2300 m above sea level!