CINCINNATI, OHIO—According to a statement released by the University of Cincinnati, evidence of a 2,000-year-old water-filtering system has been found at the Corriental reservoir in Tikal, which is located in northern Guatemala. Archaeologist Kenneth Tankersley said the crystalline quartz and zeolite detected in the reservoir’s sediments had been transported some 18 miles from the ridges around the Bajo de Azúcar. The Maya probably observed that the water bleeding out of these cliffs was clean and sweet, and associated it with the ridges’ exposed volcanic tuff, added researcher Christopher Carr. Tankersley said the Maya’s system would have removed microbes, nitrogen-rich compounds, heavy metals, and other toxins to produce pools of clean water. To read about how residents of Tikal used their land to feed the city's immense population, go to "Mapping Maya Cornfields."