Orange–Fish River Tunnel
The 3rd longest tunnel in the world
The Orange–Fish Tunnel, constructed between 1966 and 1975, is an 82.8-kilometre-long (51.4-mile) irrigation tunnel in central South Africa, built to divert water from the Orange River to the Fish River valley. It is the longest continuous enclosed aqueduct in the southern hemisphere.
Tunnel data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).