Now, as we get into 250 in the Common Era, that's considered the Classical Period. That's when some of the really great cities start to emerge, cities like Tikal and Calakmul, and my apologies ahead of time for the pronunciation. It was believed that at their peak, these cities had 50 to 100,000 people. Now, what we now believe is that it was not one unified empire, that there wasn't a Mayan empire with a centralized emperor, but rather it was closer to the Greek city-states, where each of these cities were their own state, their more powerful cities, like Tikal or Calakmul, might have had influence or sway over others, but it wasn't a unified empire in the sense of the Roman Empire or the Persian Empire or some of the early Indian Empires. Now, it is believed that each of these city-states, they did have a king who was not only a political ruler but also a spiritual ruler, considered a divine king, a connection between the natural and the supernatural, and we have evidence that they practiced human sacrifice as part of their belief system, as part of their rituals. Now, near the end of the fourth century, there's evidence that there was significant influence or even conquering of some of these cities by another civilization, or maybe we could say another city, and that is Teotihuacan. 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.