The water streaming from the caves and tunnels of Iran’s Shushtar Historical Hydraulic System looks like it is flowing through ancient tunnels created by massive worms. But actually, the elaborate system of waterworks was built by different civilizations over centuries of development.

The beginnings of the now-extensive Shushtar Hydraulics date back to the 5th century BCE, when the system was believed to have been initiated by Persian king Darius the Great. Water was diverted from the Karun River via man-made canals that sent the flow through tunnels dug through the natural rock. The complete system was likely in place by the 3rd century CE, having incorporated the work and knowhow of various civilizations including the Mesopotamians and the Romans.

Through the system of tunnels and pools, water is diverted to the city of Shushtar, powering several mills. At the time of its building the elaborate system of dams, tubes, and mills must have seemed like technological wizardry, and today it still seems amazing. The system was in use into the 20th century, providing power to Shushtar, albeit probably not as efficiently as it did before time and erosion took their toll. But considering that it was centuries old, a bit of slippage can be forgiven. Active use of the system was eventually scrapped, as its uses were replaced with more modern irrigation techniques.

UNESCO has declared the system a world heritage site, so hopefully it won’t go out of commission anytime soon. Should you ever find yourself in Iran, it’s the rare industrial site that is worth a visit.