One of the largest concentrations of rock art in Mexico is located in Mina, Nuevo León at the site known as Boca de Potrerillos.
Though it is now an inhospitable desert, this area was once a thriving grassland and wetland.1 The rock art at Boca de Potrerillos is currently thought to be around 8000 years old, though there are sites nearby that have been dated even further back.2
Boca de Potrerillos contains around 4000 rocks with 8000-10000 carvings spread along two massive crests that form the mouth of the Potrerillos canyon (Boca de Potrerillos is Spanish for “Mouth of Potrerillos.”)3
These large crests run north-south with the mouth of the canyon between them running east-west, making the entire site aligned to the cardinal directions.4
Even though there are rocks in all directions suitable for carving, almost all of the petroglyphs appear to have been intentionally carved on the eastern side of the crests, deliberately facing the rising sun. 5
Symbols associated with the Religion of the Sun such as the solar cross, spirals, suns and concentric circles are found all throughout the site. This is particularly evident in the areas where there are alignments to the solstices and equinoxes.6
At various points around the site there are large monolithic stones that appear to have been deliberately placed in specific spots to align with celestial movements. The one pictured above for example marks the northern cardinal point in the sky – the constellation Polaris.7
Another large monolith sits on an elevated spot 500m directly behind the mouth of the canyon. It’s surrounded by a cluster of petroglyphs containing images of circles and the sun.
The rock is thought to be an observation point to view the sunrise on the equinox, as the sun can be seen rising in the distance at the midpoint between the two crests of the canyon mouth when standing there on the equinox. The rock thus aligns to this distinct geographical feature where the sun rises on the equinox.8
From the same vantage point, the winter solstice sunrise can also be seen in alignment with a prominent point along the crest. Likewise, the summer solstice sunrise also aligns to a prominent point on the horizon from the same location.9
Anthropologist William B. Murray studied this site extensively, observing that the site had been used periodically for thousands of years. He noted that some petroglyphs had been carved and re-carved over time.10
Murray also speculated that the earliest inhabitants of this region could have easily traversed to and from the area by water via the Rio Grande and Mississippi drainage systems and the Gulf Coast,11 making it an accessible area for the sea-faring people who traveled by boat spreading the Religion of the Sun.
Remarkably, another site was recently discovered containing thousands of petroglyphs which are very similar to those at Boca de Potrerillos in the nearby state of Coahuila.
Here is a video of some of the petroglyphs at Boca de Potrerillos:
Turpin, Solveig A., Herbert H. Eling, and Moisés Valadez Moreno. “From Marshland to Desert: The Late Prehistoric Environment of Boca de Potrerillos, Nuevo León, Mexico.” North American Archaeologist 14, no. 4 (1994): 305-23. doi:10.2190/1vp7-2a0m-p3mm-em1l.
One such site is the La Morita rock shelter which at this point is thought to be around 12,000 years old. MURRAY W.B. 2012. — Early rock art of the Americas as reflected in the Northeast Mexican corridor. In: CLOTTES J. (dir.), L’art pléistocène dans le monde / Pleistocene art of the world / Arte pleistoceno en el mundo, Actes du Congrès IFRAO, Tarasconsur-Ariège, septembre 2010, Symposium « Art pléistocène dans les Amériques ». N° spécial de Préhistoire, Art et Sociétés, Bulletin de la Société Préhistorique Ariège-Pyrénées, LXV-LXVI, 2010-2011, CD: p. 643-654.