Which important Aztec artifact, a stone calendar, was discovered in 1790 in Mexico City?

The important Aztec artifact, a stone calendar discovered in Mexico City in 1790, was the Aztec Sun Stone.

The Mexica basalt monolith was uncovered on December 17, 1790, during repairs near Mexico City's Metropolitan Cathedral. It had been buried after the Spanish conquest, likely because colonial authorities regarded its pre-Christian imagery as pagan. The sculpture is about 3.6 meters in diameter and nearly a meter thick.

Its concentric carvings depict Mexica ideas about cosmic time, including the central solar deity and symbols associated with the Five Suns. Although commonly called the Aztec Calendar Stone, it was not a practical calendar like a modern wall calendar. Scholars debate some details of its imagery and purpose, and the name “Sun Stone” is generally preferred today.

The stone was displayed publicly on the cathedral before moving to Mexico's National Museum in 1885. Since 1964, it has been one of the best-known objects in the National Museum of Anthropology. It is often confused with the Tizoc Stone or the monumental Coatlicue statue, which are separate Mexica works.