M62 Scammonden Dam

Thousands drive over it every day, but don't give it a second thought.
Excavations for the dam started in 1966.
Water started to fill the reservoir in July 1969. 
By October, it held around 1,800,000,000 gallons of water. 
The motorway opened Dec 1970 - Scammonden Dam was the first dam in the world to carry a motorway – and it's still the only one in Britain.