Cerro Pachón (Spanish for "Pachón hill") is a mountain located close to Chilean city of Vicuña and 10 km southeast of the Cerro Tololo Inter-American Observatory, at an altitude of 2,715 m over the sea level in the foothills of the Andes. The location is exceedingly dry, making it suitable for infrared observations. The air overhead is very stable, yielding excellent seeing.