Archaeologists have uncovered a rare scorpion-shaped mound in Mexico’s Tehuacán Valley that was likely used to allow ancient Mesoamerican farmers to track the sun’s path during the summer and winter solstices. The earthen structure, about 205 feet (62.5 meters) long, likely dates to between CE 600 and 1100 and highlights how local communities blended astronomy, farming, and rituals.

Map depicting the scorpion effigy mound and the probable sun paths during the summer and winter solstices. Credit: J. Neely et al., Ancient Mesoamerica (2025); CC BY 4.0

The mound, which has been documented in prehistoric irrigation canal surveys about 160 miles (260 kilometers) southeast of Mexico City, forms a clear scorpion shape with a body, pincers, and a curved tail that ends in a raised “stinger.” Built using stones and soil up to 31 inches (80 centimeters) high, it has remained remarkably preserved. Excavations revealed ceramic jars, tripod molcajetes for grinding, incense burners, and a hollow figurine fragment, which point to ritual activity related to farming and seasonal change.

Researchers believe that the mound was part of a larger civic and ceremonial complex occupying about 22 acres (9 hectares). Twelve other mounds lie nearby, integrated within a network of irrigation canals that supported intensive agriculture. The scorpion-shaped mound, however, is an intentional effigy—a symbolic structure of relatively uncommon occurrence in Mesoamerica. Effigy mounds are common elsewhere in North America but extremely uncommon here, so this find has particular significance.

The mound’s alignment appears to be intentional. The direction it faces—east-northeast—matches the sunrise during the summer solstice when viewed from the “stinger” to the left claw. During the winter solstice, observers standing closer to the left claw would be able to see the sunset align with the tail. All of this would have helped early farmers identify transitions in seasons, indicating the start of the rainy season and the best times for planting.

PH๏τos of the molcajete offering. Left: the offering as it was found; Right: cover bowl removed. Credit: J. Neely et al., Ancient Mesoamerica (2025); CC BY 4.0

The scorpion’s symbolic position in Mesoamerican belief systems adds another layer of meaning. It was identified with Tlāhuizcalpantēcuhtli, the god who represents Venus—the morning star—ᴀssociated with rain and fertility. The design of the mound may therefore have been both cosmic and agricultural in its signification, serving as a ritual place to appeal for rainfall and good harvests.

Ceramics at the site suggest connections to Cacaxtla, a nearby regional center that also features scorpion and Venus imagery in murals. This connection could reflect shared religious or political traditions in central Mexico during the Epi-Classic period.

A to-scale rendering of the Scorpion Mound, generated during the 2000 field season in the Tehuacán Valley. North is magnetic. Credit: J. Neely et al., Ancient Mesoamerica (2025); CC BY 4.0

Compared with monumental urban temples, the Scorpion Mound is a testimony to the engagement of a rural community with celestial knowledge. Its builders were most likely farmers who observed the sky not in elite-controlled observatories but from lands thoroughly tied to water and cultivation. The structure may be proof of an egalitarian expression of astronomical and ceremonial practice in everyday life.

Archaeologists have scheduled further excavations to confirm the construction phases of the mound and further test its solstice alignments.

More information: Neely, J., Castellon-Huerta, B., Wilson, S., Willis, M., & Walker, C. (2025). The scorpion mound complex: An effigy mound site with possible functional/ceremonial significance in the Tehuacán Valley of Puebla, México. Ancient Mesoamerica, 1–16. doi:10.1017/s0956536125000070