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Monticello Dam
Monticello Dam is a 304-foot (93 m) high concrete arch dam in Napa County, California, United States constructed between 1953 and 1957. The dam impounded Putah Creek to create Lake Berryessa in the Vaca Mountains.
Lake Berryessa is currently the seventh largest man-made lake in California. Water from the reservoir primarily supplies agriculture in the Sacramento Valley downstream.

haha and the wiki bot filled in the rest of the picture lol...

except the part that brought us there to begin with!

haha true, hint will be out tomorrow evening my time :D