MEXICO. Oaxaca. October 27, 2019. Hierve el Agua is a rock formation and mineral water spring in the mountains of Oaxaca, now a tourist attraction but around 2,500 years ago a sacred site for the Zapotecs. In 1990 two artificial pools were constructed to enhance the appeal of this confirmed archaeological site, known for one of the world’s oldest irrigation systems. Ongoing conflicts among local communities persist over the right to exploit this attraction in one of Mexico’s poorest areas.