Within the desert of Tabernas there is an oasis. This spot was originally used for Lawrence or Arabia, thus Sergio Leone probably picked this spot because of his admiration of director David Lean.
In For a Few Dollars More this location represents Las Palmeras, the place where Indio and his men meet up after the bank raid of El Paso. This location is unspoiled by time and man, looking virtually the same half a century later!
Indio's gang shoots open the cabinet
The safe is revealed (and has since become a great bush!)
Full size images below. Click to enlarge.
To get to the Oasis, you must walk through one of the many ramblas in Tabernas. These ramblas and plateaus above were often used in many westerns. Examples below.