According to the University of Cincinnati, ancient Maya built sophisticated water filters in the once-bustling city of Tikal using natural materials they imported from miles away. A multidisciplinary team of UC anthropologists, geographers and biologists identified crystalline quartz and zeolite imported miles from the city. Both minerals are used in modern water filtration. The filters would have removed harmful microbes, nitrogen-rich compounds, heavy metals such as mercury and other toxins from the water. This is one of the oldest water treatment systems of its kind in the world and the system would still be effective today after more than 2,000 years ago.