Puente del Inca (English "Bridge of the Inca") is a natural arch that forms a bridge over the Las Cuevas River, a tributary of the Mendoza River. It is located near the small village of Puente del Inca, in Las Heras Department, Mendoza Province, Argentina. The nearby hot springs are also named Puente del Inca.
Both glaciers and the hot springs were involved in the formation of the arch. During an ice age, glaciers would have expanded down throughout the entire valley; then, at the end of the ice age when the Earth began to warm up again, the retreating ice would have left behind massive piles of eroded debris. The water that flows from the hot springs is extremely rich in mineral content, to the point that it has been known to petrify small objects in a layer of minerals. Similarly, the piles of debris left by the glaciers were encrusted over time into a single solid mass. Finally, during a period where the climate was extremely wet, a powerful river formed in the valley. It cut a channel through the lower, least encrusted layers of debris, which gradually eroded into the large opening of the arch. (Wikipedia)