Episode three begins in Quito, Ecuador, and relates the amazing story of the 16-month Spanish expedition (1541-42), led by Gonzalo Pizarro, to find El Dorado, the mythical land of gold. Crossing the Andes with pack animals, Wood and his team hack a path through the forests, following in Pizarro's footsteps to the Coca river, where they build a balsa raft and sail down to the river Napo, following the route of the conquistadors. There, on Christmas day 1541, the Spanish expedition split, with 60 men under Francisco Orellana sailing (contrary to orders) all the way down the Amazon to the sea in a makeshift boat: an achievement that was "less of a journey, more of a miracle." They were the first outsiders to see the interior of Amazonia and the first to discover and travel the length of the river. On their journey, they encountered unknown empires and vast populations that were later wiped out by disease and subsequently forgotten. The program recounts Orellana's story, as well as the tale of the retreat of the army, under Orellana's cousin and boyhood friend, Gonzalo Pizarro, an almost Shakespearean tale of revenge recorded in their letters and the diary kept by the expedition.

• Michael Wood