The ancient structure believed to have been built as a celestial observatory by the Mayans is the temple of El Caracol, located in the archaeological site of Chichen Itza in Mexico. Its distinctive round shape and window alignments suggest its purpose as an astronomical observatory where the Mayans tracked celestial bodies, including the movements of the sun, moon, and stars. Scholars believe that it played a significant role in the Mayans' agricultural calendar and religious practices. This sophisticated understanding of astronomy highlights the complexity of Mayan civilization, showcasing their advanced knowledge and skills in mathematics and architecture.