If you've traveled to Mexico City lately and landed at the airport, you probably noticed an unfortunate stench. AP Reporter Olga Rodriguez wrote about the persistent odor earlier this week and says that it "wafts from the manholes and leaves the morning air smelling fresh as a septic tank."

The unpleasant smell both bothered -- and intrigued -- Rodriguez every time she went through the airport, so she had to get to the, um, bottom of its cause.