Teotihuacan is an ancient Mesoamerican city located in a sub-valley of the Valley of Mexico, which is located in the State of Mexico 40 kilometres (25 mi) northeast of modern-day Mexico City. Teotihuacan is known today as the site of many of the most architecturally significant Mesoamerican pyramids built in the pre-Columbian Americas. At its zenith, perhaps in the first half of the first millennium CE, Teotihuacan was the largest city in the pre-Columbian Americas, with a population estimated at 125,000 or more, making it at least the sixth-largest city in the world during its epoch. After the collapse of Teotihuacan, central Mexico was dominated by the Toltecs of Tula until about 1150 CE.