archaeologist dolph widmer has studied teotihuacan for more than a decade. amazing things about teotihuacan is that it's a city. and even though right now it's an agricultural field -- you see cactus everywhere -- you can still tell it's a city because the surface of the ground is littered with artifacts. they're everywhere. we can see that we have a site. here i have cultural material, like this piece of obsidian. i have a piece of ceramics. all this stuff here tells me that people lived here. and by noting the artifacts on the surface, i can get an idea how big their residences were, how many residents there were in the city, as a whole, and get some idea of the size and number of people that lived here. keach: during the 1960s, archaeologists surveyed the entire city, revealing an urban grid as deliberate as the streets of manhattan. a total of 2,600 buildings lined densely packed streets. 80% of these were residential compounds. these compounds enclosed numerous sleeping rooms, patios and kitchens. archaeologists estimate that 30 to 100 people could be h

but for archaeologist dolph widmer, it was an opportunity. when the roof collapsed, it did something wonderful. it collected for us, in place, in the place that they were originally used, a whole series of artifacts and tools. and these were found right here in this room. this room has sealed underneath this collapsed roof the first evidence we've ever found of the production of elite craft items -- items such as shell, jade, other exotic materials. on this bench we found three ceramic vessels, and the vessel over here had a quiver of tools in it. we found bone tools and chisels. also, we found numerous other artifacts in their original places, just like they were being used. and this "pompeii effect," if you want to call it, is very exciting to us. for the first time we had, captured and preserved right before us, a mayan artisan workshop. keach: in the workshop were 10 obsidian saw blades. obsidian is a natural volcanic glass. the artisans would have used the blades to cut and saw. i suspect that saws were taken and mounted into a handle so