The Art Archive/Bibliothèque des Arts Decoratifs Paris/Dagli Orti

Like many travelers to Petra, Roberts marveled at the ancient city’s spectacular Khasne (Treasury), a 65-foot-high colonnade building decorated with scenes of Greek and Nabatean mythology. “I cannot say,” Roberts wrote, “whether I was most surprised at the building or its extraordinary position. It stands…in an immense niche in the rocks.”