Over two thousand years ago, in central Mexico, one of the largest and most sophisticated cities of the ancient world emerged. Its builders brought urban planning to a remarkable level of refinement: the layout followed precise astronomical principles and organized more than two thousand residential compounds into neighborhoods defined by trade, ethnic origin, and other criteria—many with their own temple and plaza. At its height, Teotihuacan was home to somewhere between one and two hundred thousand people, and maintained active ties with numerous cultures across Mesoamerica. Yet despite everything that is known today, the city is still shrouded in mystery. Teotihuacan is not a solved enigma; it's a living place, constantly being rediscovered—and you, visiting it now, are part of that ongoing story.