New York City’s Water Tunnel No. 3 began construction in 1970 and will not be completed until at least 2020. This tunnel was featured in Die Hard with a Vengeance.
I can’t think of any current construction project with a longer schedule. 50 years may not be a lifetime. But it’s close.
I forgot about that project 50 years is a very long time. I am surprised we started it.
Cooridor H in West VA.
The “Duomo” cathedral in Milan (Mediolanum, to the Romans) was begun in th 5th century, and, although mostly complete by the 1890, it is still under contstruction.