Good Dam! that's a big lump of concrete

Hoover Dam to be specific. Upto 5500 people working for 4 years, came in 2 years ahead of schedule, paid for itself with the electricity generated as a byproduct - its main aim was flood control and irrigation - and expected to last 2000 years. Methinks project management has lost something in the intervening 80 years...

Avec waterslide - the arizona side spillway only used of the water levels rise faster than the turbines can cope with. Only used twice to date, 50 ft diameter pipe bypasses the turbine hall