Teotihuacan

One of the largest cities in the ancient world at its height around 450 CE, Teotihuacan in the Basin of Mexico covers over 20 square kilometers and was home to a population of perhaps 125,000. The Avenue of the Dead connects the Pyramid of the Moon to the north with the Pyramid of the Sun — the third largest pyramid in the world — and then continues south to the Feathered Serpent Temple. The geometric precision of the street grid, aligned to astronomical observations, and the sheer scale of the monumental core remain striking to modern visitors.