From the crowded, horse-smelly bridge, the path drops sharply down over the lip of the dam into Petra’s most dramatic and awe-inspiring natural feature – the Siq (meaning “gorge”), principal entrance into the city, yet invisible until you’re almost upon it.
The Siq was formed when tectonic forces split the mountain in two. The waters of the Wadi Musa subsequently found their way into the fault, laying a bed of gravel and eroding the sharp corners into curves as smooth as eggshell, helped by the cool winds that blow in your face all the way down. At the entrance to the gorge, the path was originally framed overhead by an ornamental arch, which collapsed in 1896 although its abutments survive, decorated by the smoothed-out remnants of niches flanked by pilasters.
The path along the wadi bed twists and turns between high, bizarrely eroded sandstone cliffs for 1.2km, sometimes widening to form broad, sunlit open spaces in the echoing heart of the mountain, dotted with a tree or two and cut through by the cries of birds; in other places, the looming 150m-high walls close in to little more than a couple of metres apart, blocking out sound, warmth and even daylight.
All the way along the left-hand wall is a Nabatean rock-cut water channel, and on the right-hand wall you’ll see the remains of terracotta pipes for water, both probably dating from the same time as the reorganization of the city water supply that prompted the building of the dam. At various points, you’ll be walking over worn patches of the Roman/Nabatean road which originally paved the Siq along its entire length, in between stretches of newly consolidated pathway. High, narrow wadis feed into the Siq from either side, most of them blocked by modern dams (often set back to show the remains of the original Nabatean dams) to limit both flood danger and unauthorized exploration: once you’re in the Siq, the only way is onward or backward.
Dotted along the walls at many points are small votive niches, some Greek-style with pediments, others with mini god-blocks. After about 350m, a small shrine has been carved on the downhill side of a freestanding outcrop of rock, with two god-blocks, the larger of which is carved with eyes and a nose. A little further on, on the left-hand wall at a sharp right-hand bend, is a merchant in Egyptian-style dress leading two large camels; the water channel originally ran behind all five sets of legs, and it’s just possible to trace the worn outline of the camels’ humps in the rock wall.
When you think the gorge can’t possibly go on any longer, there comes a dark, narrow defile, framing at its end a strip of elegant classical architecture. With your eye softened to the natural flows of eroded rock in the Siq, the clean lines of columns and pediments come as a revelation. As you step out into the daylight, there is no more dramatic or breathtaking vision in the whole of Jordan than the facade of the Treasury.