- The Inverted Syphon was a technique for getting an Roman Aqueduct to cross a valley without using a bridge.
Aqueduct du Gier
- The Aqueduct du Gier, was a Roman Aqueduct in Gallia Lugdunensis, which brought water 26 miles (42 km) to Lyon.
- It used four Inverted Siphons and eleven tunnels and was completed in c. 50 CE.
- Instead of building bridges across the river valleys, the aqueduct used four inverted siphons to cross the valleys of the rivers Dureze, Garon, Yzeron and Trion.
- The water would enter a water tank in a sunken Castellum or tower before flowing through pipelines that descended to the valley floor.
- The pipes then crossed over the river on arches and rose up the other side to another water tower that was slightly lower than the first tank.
- This avoided having to build vast bridges such as the Pont du Gard Roman Aqueduct.
Aqueduc du Gier, France