From the Abra del Acay pass (just under 5,000 m), you can reach Ruta Nacional 40 (the highest road in Argentina, a gravel road) through breathtakingly beautiful mountain scenery in the valley of the Río Calchaquí. In the further course you cross this mountain river several times through broad fords; it is hard to imagine that someone comes through here with a dry foot. Finally, a wide plain opens up to admire giant cacti.