Tourists walk past a lone olive tree along the ancient trade road through the Siq, the path into the Nabatean capital at Petra, Jordan. This ancient road, originally paved by the Nabateans and later renewed by the Romans, passes for about 1.2 km through this natural stone valley. Note that this is not a canyon carved by water, but a divide created by tectonic forces. Note the matching rock grain on both sides of the path. © Rick Collier