Final answer:
The Aztecs used astronomical observations to plan their city locations, integrating religious, calendrical, and practical purposes such as navigation and timekeeping into their urban design and enhancing the rulers' authority.
Step-by-step explanation:
The Aztecs utilized astronomical observations in planning the locations of their cities primarily for religious and calendrical purposes. By aligning their buildings and the layout of their cities with celestial events, such as the solstices and equinoxes, they were able to create calendars, schedule agricultural activities, and plan religious ceremonies. Moreover, these alignments often enhanced the rulers' authority by connecting them with the divine, and provided practical benefits such as navigation and timekeeping. For instance, the great city of Tenochtitlan, which is located on the modern-day site of Mexico City, was designed with its major temples and complexes organized on a north-south axis to reflect this connection to celestial movements.
Outer space, cosmic events, and celestial bodies were deeply integrated into their daily lives, governance, and their spiritual understanding of the world. The urban design of Tenochtitlan, with its symmetrical layout, not only served a religious purpose but also showcased a sophisticated level of engineering and knowledge of astronomy at the time. These practices echo those of other ancient civilizations, such as the Maya and the inhabitants of Teotihuacan, who also constructed their cities with astronomical precision.