Guatavita is a small green lake set in a crater in the hills north of Bogotá. The fact you need to climb up to this very circular body of water is somewhat strange: it doesn’t seem quite natural, and no one really knows how it was formed. A meteorite, maybe? A sink-hole, possibly? More surprising, is that this chilly pond only 300 metres wide spawned the legend of El Dorado, a myth so potent that for four centuries it drove gold-crazed explorers in to every corner of the continent (and many to early graves) and passed into the English language as the lost city of fabled wealth.