Tupungato, one of the highest mountains in the Americas, is a massive Andean lava dome dating to Pleistocene times. It lies on the border between the Chilean Metropolitan Region (near a major international highway about east of Santiago) and the Argentine province of Mendoza, about south of Aconcagua, the highest peak of both the Southern and Western hemispheres. Immediately to its southwest is the active Tupungatito volcano (literally, little Tupungato), which last erupted in 1987.