Siq, City of Petra, Jordan
The main entrance to the City of Petra in Jordan is a slot canyon. The Siq, translated literally to The Shaft, is a three-quarter-mile long narrow gorge, sometimes no more than 9.8-feet wide, that leads visitors to Al Khazneh, or The Treasury (pictured here), which is Petra's most elaborate ruin. The walls range from about 300-600 feet in height. While most slot canyons are formed by water erosion, The Siq has a unique natural history. It is a geological fault that was split apart by tectonic forces and only later smoothed by water. Remains of ancient constructions around the slot canyon include two abutments and some hewn stones of a once-monumental archway for the grand entrance to the city, votive niches, several underground chambers, and a group of statues that, while heavily eroded, still reveal two merchants leading camels.