It turns out there was a real-life city of El Dorado – Taghaza. Only, it was built with salt instead of gold (Ibn Butata, 14th century AD):
It is a village with no good in it. Among its curiosities is the fact that the construction of its houses and its mosques is of rock salt with camel skin roofing and there are no trees in it, the soil is just sand. [COMMENT: Herodotus reported the same thing in the 5th century BCE.] In it [the village] is a salt mine. It is dug out of the ground and is found there in huge slabs, one on top of another as if it had been carved and put under ground. A camel can carry two slabs of salt. Nobody lives in it except the slaves of the Massufa who dig for the salt and live on dates brought to them from Dar’a and Sijilmasa, and on the meat of camels…
In ye olden days, salt was an intensely valuable commodity – the source of preservation of foods – so a city made of salt would be quite the sight! Of course, it was windswept and dirty and dingy. You read quite often that the Taghazans would exchange salt for its weight in gold, but Kurlansky claims this is a myth based on the style of barter (Salt, pg. 49). Regardless, my guess is its value as a commodity would make the buildings worth plenty.
Unfortunately, there are no pictures of the city because it was destroyed in 1591 by the Moroccan Pasha. THE END.
My Name Is Legion 