The search for gold and for the mythical El Dorado gripped the imagination of the conquistadors from the beginning of the sixteenth century. Crossing over the Andes, they explored the unknown eastern forests and jungles, launching expeditions that were often disastrous and always disappointing. As the range of exploration expanded, El Dorado retreated, always just beyond the horizon. The last goal of these explorations was the land of the Mojos, a land located in the upper Amazon basin and which lies many months of the year submerged under water. It is a mysterious land and, as legend had it, inhabited by a people rich in gold and precious stones. Yet all the Spaniards found – as narrated in these compelling pages – was a limitless swamp, sparsely inhabited by a small number of people and so ill suited to usual system of productive forced labor. It was the Jesuits instead who established here a network of missions second in size and population only to that or Paraguay and so went in search of souls rather than gold.