Hoover Dam has million visitors by now.
http://www.usbr.gov/lc/hooverdam/service/index.htm l
It is an engineering hall of fame design and work worth for many to follow the design even now. You can't beat it, you can't forget its site, worth seeing once a life time.
They even cooled the concrete to make it harder on solidification. It is highly artistic design and has a gold look. It also generates lots of energy and yet remains protected from high speed water fall. It is like, one is not a Civil Engineer if one does not know the Hoover Dam.
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Prof. (Dr.) Shyam, Managing Director for Sensors Technology Private Limited. Gwalior, MP474001, India.