I'm sitting in the shade of a 1,100 liter water tank on the roof of a three story apartment house overlooking what seems to be a middle class neighborhood just south of downtown Oaxaca City, Oaxaca.

Across the street behind me stands a massive supermarket where you can buy everything from cell phones and pizza to dead animal legs and household petrochemicals. It's always 15 degrees colder in there than the busy streets outside.