Moderately repulsive thing on Roman sewer full of human excrement and some moderately interesting other things. I recently saw an entire highly scientific book on coprolites and the archaeological usage of human excrement to understand things about the past; I cannot say that I would wish to specialize in this, but what the heck.
You'd be amazed what you can learn from it! One of my friends has pretty much made his career from human waste of different sorts! I'm an archaeologist by qualification, but defected to anthropology pretty quickly... A lot of my friends didn't and they seem to thoughly enjoy wading knee deep through it at some points.
On a completely unrelated point I once knew a girl who differentiate between London's stratographic layers just by how coarse, or not, the brick dust was! I found it amazing, that has to be the best archeo-geek party trick! And I speak as one...