From Smithsonian Magazine (hat tip: Dan Franke):
More than 2,000 years ago, the Maya built a complex water filtration system out of materials collected miles away. Now, reports Michelle Starr for Science Alert, researchers conducting excavations at the ancient city of Tikal in northern Guatemala have discovered traces of this millennia-old engineering marvel.
As detailed in the journal Scientific Reports, the study’s authors found that the Maya built the Corriental reservoir filtration system as early as 2,185 years ago, not long after settlement of Tikal began around 300 B.C.
The system—which relied on crystalline quartz and zeolite, a compound of silicon and aluminum, to create what the researchers call a “molecular sieve” capable of removing harmful microbes, heavy metals and other pollutants—remained in use until the city’s abandonment around 1100. Today, the same minerals are used in modern water filtration systems.
More at the link.