Teotihuacan

Teotihuacan is an ancient Mesoamerican city located 40 km northeast of modern Mexico City. Settled by 400 BCE and peaking around 500 CE, it covered 20 sq km with a population estimated at 125,000-200,000, making it one of the world's largest cities. The site features the Pyramid of the Sun, the Pyramid of the Moon, and the Avenue of the Dead stretching 1.5 miles. Designated a UNESCO World Heritage Site in 1987, the city was destroyed by fire around 750 CE, possibly during civil unrest. Over 95% of the ruins remain unexcavated.