We know that it was a very powerful city and that in the fourth century, it started to really exert significant influence, and just to get a sense of the sophistication of what Mayan cities look like, and I'll show you what we believe Teotihuacan looked like in a second, but this is a construction of what Tical might have looked like near its peak, and Teotihuacan, we have significant ruins there. Teotihuacan, as you can see, is based near modern-day Mexico City, and these are the ruins from Teotihuacan, and just to get a sense of how sophisticated a city this was, this is a reconstruction of the map of the city, so the vantage point that you have from this picture would have been roughly in that area, so what you're seeing right over here are these buildings or these little squares here, this pyramid that you see out in the distance, that would have been this pyramid, and so you can see from this reconstruction of what the city might have looked like, it was a vast and significant city. Pretty much everything that you can see in this picture was part of this great city, and it was believed that it was established around 150 BCE, based on our best evidence today, and lasted until about the middle of the sixth century. Now, the name Teotihuacan, that's not its original name. It's the name given to it by the Aztecs, but it's believed that at its peak, around 400, 450, and remember, this is around the time that it was exerting significant influence over the Mayans, it is believed that it had upwards of 100,000 people living in the city, 100,000 to 200,000, I've even seen some accounts saying 250,000 people, which would have made it, at the time, one of the largest cities in the world. Some accounts have it ranked as the sixth largest city in the world that we know about. Now, one interesting question was, was Teotihuacan an independent city-state by itself, or was it the center of an empire?