The path narrows to 20 feet in width at times and the walls are several hundred feet tall. Waves of color swirling through the rock face in the Siq, as in all of Petra, range from pale gold and white to shades of pinks and rich reds to chocolate brown. Petra's position as a trading post depended on the availability of water, and Nabataean traders were expert hydraulic engineers. Catchment basins for water runoff, underground channels, as well as cisterns to house water are found all over the site, and canals carrying water from nearby springs in terra-cotta pipes are carved into the sides of the Siq. In Roman times, the great gorge's path was paved with stone.
Some parts recently uncovered by excavations remain visible today.
Carved indentations in the walls served as altars to the Nabataean's chief deity, Dushara. They are probably abstract representations of Dushara or other Nabataean deities. Just when it seems as if the Siq will never end, you catch a glimpse of the most amazing site of Petra through an opening as wide as two horsemen abreast. The salmon-colored edifice stands 120 feet high, a stunning example of Hellenistic architecture with graceful Corinthian columns. Although used as a royal tomb, the structure is called the Treasury.