Discover El Dorado
This achievement was added in a patch in conjunction with the Spain and Inca DLC. It does not require the DLC, however.
The El Dorado natural wonder randomly appears in the game. It is one of the rarer natural wonders, but it may appear in any normal random map. It frequently appears in the Conquest of The New World scenario.
El Dorado is found only in forest and jungle tiles. The quickest way to find it is to start a game on a huge skirmish map with jungle as the primary terrain, and starting in the Information Era. When the game begins, adopt all of the social policies in Rationalism, which will grant you a free technology. Research Satellites to reveal the entire map. If El Dorado is one of the natural wonders, you will gain the achievement immediately. If not, quit to main menu and repeat the process.
Refers to Sir Walter Raleigh, who set off on an expedition to find El Dorado.