On February 21, 1978, workers laying underground power lines in central Mexico City uncovered the Coyolxauhqui Stone, a monumental Aztec artifact that depicts the dismembered goddess Coyolxauhqui. Initially thought to be just another carved stone, its significance became apparent as it was revealed to be part of the Templo Mayor, the central ceremonial pyramid of the Aztec capital, Tenochtitlan. This discovery transformed archaeological understanding of the site, which had previously been thought to be largely destroyed during the colonial period following the 1521 conquest. The Coyolxauhqui Stone, measuring over 10 feet in diameter, provided crucial evidence of the sacred district's preservation beneath modern urban development. The stone's iconography reflects the complex relationship between sacrifice, politics, and cosmology in Aztec society. Following this discovery, extensive excavations led by archaeologist Eduardo Matos Moctezuma revealed additional artifacts and structures, demonstrating that significant portions of Tenochtitlan remain intact beneath the bustling metropolis. This find not only reshaped the understanding of Aztec history but also highlighted the coexistence of ancient and modern urban landscapes in Mexico City.