Hierve el Agua (literally "boiling water", although the springs are not thermal) is a limestone "waterfall" formed by mineral springs at the top of the cliff trickling over the edge over thousands of years. This was the last stop on our day tour.
The next day we took the public bus up to Llano Grande, a town of 140 people in the Sierra northeast of Oaxaca, for a couple days in nature.
Click the thumbnail to see the full image.