This is admittedly a bit of a drive, and makes the most sense if you’re headed towards Altar or Caborca anyway.

Cross the border at Nogales, drive south on Highway 15 to the junction town of Santa Ana, and turn west on Highway 2. Part way to Altar you cross a low range of hills and see a sign pointing south (left) to TRINCHERAS. It’s a dirt road, but usually is kept in good shape. As you drive south, you’ll see a high, dark hill. This is el Cerro de las Trincheras (the Hill of the Fortifications), and the whole side you see is one big archaeological site.

The hill is made of volcanic rock, covers over 230 acres, and stands about 450 feet above the valley floor. Its north slope is covered with stone terraces, the walls of which are fairly low at the base of the hill, but rise to nine feet high towards the summit. The entire site contains more than nine hundred such terraces.

Who built it and why? Earlier explanations went from a defensive position, to a city of refuge in troubled times, to a terraced farm site. Excavations in the 1990s by the University of Arizona, however, revealed that the site was a large town with a population of 1,000 or more, and was occupied from around 1300 to 1450 AD. It was divided into districts, at least one of which specialized in making shell bracelets.

Status seemed to increase as one went higher, with the elites probably living at the summit, where there is a spiral, walled enclosure called el caracol or “the snail shell”, probably built for religious purposes. A larger public space called la cancha — “the court” exists near the base of the hill. This was open to the sky, and probably viewable from all over the north slope of the site. Residents farmed agaves on the lower terraces and corn, beans and squash in the adjacent river valley.

The first European to visit and write about the site was Lieutenant Juan Mateo Manje, who passed by there with Father Kino on Sunday, February 22, 1694. (I’ll write more about Manje in a later blog.) He was told that the site was used as a refuge area. This may well have been the case in human memory, as by Manje’s day the town on the hill had been abandoned for over two hundred years.

Trincheras also boasts a painting of the Virgin of Guadalupe partway up the north slope of the hill, with a well-worn trail leading to it. It is also believed by many to have been the birthplace of the historic/legendary bandit/resistance fighter of the California Gold Rush, Joaquin Murrieta.