What is the name of the massive carved stone calendar discovered in Mexico City?

The massive carved stone calendar discovered in Mexico City is called the Piedra del Sol, or Aztec Sun Stone. It is a late Mexica basalt monolith and one of the most famous surviving works of Aztec sculpture.

The stone was discovered on 17 December 1790 beneath Mexico City’s central plaza, now the Zócalo, during colonial public-works repairs. The Spanish had buried it after the conquest, and it remained underground for nearly three centuries. After its discovery, it was mounted on the exterior of Mexico City Cathedral, where it stayed until 1885. It is now displayed at the National Museum of Anthropology.

The monolith measures about 3.6 meters across and is nearly a meter thick. Its carved rings include day signs, cosmological symbols, and imagery associated with the Mexica conception of time and the successive eras of creation. Its central figure has been interpreted in different ways, including as Tonatiuh or the earth deity Tlaltecuhtli.

Despite its nickname, the Sun Stone was probably not a simple working calendar or sundial. Some scholars interpret it as a ceremonial monument, possibly connected with ritual sacrifice. It is also frequently—but imprecisely—called the Aztec Calendar Stone.