Teotihuacan was one of the most influential cities of ancient Mesoamerica, reaching its height between the 1st and 7th centuries AD. Known for its vast ceremonial complex, it features the Pyramid of the Sun, the Pyramid of the Moon, and the Avenue of the Dead. The city's original inhabitants remain uncertain, but it had a profound impact on later cultures, including the Maya and the Aztecs, who revered it as a sacred place. Its well-planned urban layout and extensive murals suggest a highly organised society with complex religious and political structures. The Aztec New Year, or Yancuic Xihuitl, is celebrated on 12 March in the modern Nahua tradition. The date is based on the ancient Mesoamerican calendar system, which differs from the European calendar but marks the renewal of the solar cycle, a concept deeply connected to the astronomical alignments and ritual practices seen at Teotihuacan.