Aguirre, der Zorn Gottes (Aguirre, the Wrath of God), 1972.
Another excellent film by Werner Herzog staring Klaus Kinski.
Set in the 16 century and based on records that suggest this may actually have occurred, the film re-enacts the journey taken by an army of Spanish conquistadors through the Andes in search of the mythical El Dorado, the City of Gold. Kinski is as crazy as every, and was well cast as the merciless, power hungry Aguirre, leading his army – and his lovely teenage daughter to their deaths. The scenery is breathtaking as you would expect and the film is an interesting for-ray into the dark side of human nature.
The DVD I watched also had an excellent director commentary, which is also worth listening to.