Yes, The City Of Gold, or more accurately know.
The City Of El Dorado.
Which, literally means, The Gilded One.
The Incan's, Aztec's or whichever native tribes in the area were great smiths, and what you would call, alchemists.
Except it wasn't lead to gold, it more like, make an alloy of copper and gold, which is quite reddish, look like pure gold, through chemical means, which, I think was a solution that eroded the top layer of copper, but I can't be relied on for the chemical bit.
It has been scientifically proven, and also archaealogically.
So, there you have it, the city of gold, which was looted by Spaniards, only for them to find that the gold was infact very unpure.