These are the Trincheras hills. With the lush vegetation it's hard to see the rock walls that traverse the hillside. Trincheras was named for El Cerro de Trincheras, a nearby archaeological site. This site is also the namesake of a distinctive type of archaeological site found in the desert basins of the southwest United States and northwest Mexico. Remains of hillside terraces and walls reminded early explorers of "trincheras," the Spanish term for entrenchments or fortifications