Holding back an enormous reservoir, the dam was built in the face of strong opposition from critics who gave warning, among other things, that it would be vulnerable to earthquake damage that might cause disastrous floods.

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Nietzel says the most common place the clues about "where warm waters halt" first lead people is to Eagle Nest Lake, about 100 miles north of Santa Fe, because it has a dam that holds back warm water and is known for its brown trout.

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And the major part of the project is a huge dam called the Cofferdam, which has been built to hold back the water from the docks.

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But back in 1963, while the reservoir dam in Cwm Tryweryn was still under construction, it was the actions of three young men that were making the headlines.

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