Some of the arguments for empire, it seemed like there was wealth. It seemed like they were able to build large infrastructure works. There was consistency across different settlements. Now, there's also the Tiwanaku. And we believe it was truly an empire, but we could say the Tiwanaku civilization, right over here in yellow, really centered at off the coast of Lake Titicaca, which is right in that area right over here. But the big takeaway here is this is just a sample of some of the civilizations that you've had in this part of the world. Now, what's really interesting is, as I mentioned, a lot of them weren't able to form formal empires, people think, because of the valley, the mountains, the terrain, that were keeping people from maybe trading or being able to control each other a little bit more strongly.