The Siq Canyon Entrance, Petra, Jordan — The narrow 1.2-kilometer gorge leading to Petra was formed by tectonic forces splitting the sandstone massif, then widened by the Nabataeans who also lined it with channels carrying water into the city. At its narrowest the walls close to just 3 meters apart, framing a dramatic first glimpse of Al-Khazneh at the canyon's end.
© Diego Delso, CC BY-SA 3.0, via Wikimedia Commons
