El Dorado, just like the legend says, is a natural wonder which is found exclusively in deep forests or jungles. This makes it quite difficult to find - while mountain wonders like Mt. Kailash and Sinai are spotted from a great distance (being mountains), to find El Dorado your Scouts have to venture into the most impassable terrain and get almost next to the wonder's tile to spot it. Of course, the 500 Gold reward for finding it first is well worth the trouble, especially in the early game!
This fabled "Lost City of Gold" drew many Spanish conquistadors to the New World, all hoping to stumble upon its untold riches. For nearly three centuries, the myth of precious gems and gold drew explorers to the South American coasts, who often sacked other cities they found along the way. El Dorado has captivated explorers throughout the centuries, and expeditions as late as 1804 were arranged to divine its location. However, it is now believed that the mythical city was inspired by the name of a Muisca chief, who reportedly, as part of an initiation, covered himself in a fine layer of gold dust and dove into the Guatavita Lake.