Pliny the Elder and other writers identify Petra as the capital of the Tadeanos and the center of their caravan trade. Enclosed by towering rocks and watered by a perennial stream, Petra not only possessed the advantages of a fortress, but controlled the main commercial routes which passed through it to Gaza in the west, to Bosra and Damascus in the north, to Aqaba and Leuce Come on the Red Sea, and across the desert to the Persian Gulf.
The narrow passage (Siq
) that leads to Petra
Excavations have demonstrated that it was the ability of the Nabataeans to control the water supply that led to the rise of the desert city, creating an artificial oasis. The area is visited by flash floods, and archaeological evidence demonstrates the Nabataeans controlled these floods by the use of dams, cisterns and water conduits. These innovations stored water for prolonged periods of drought and enabled the city to prosper from its sale.
In ancient times, Petra might have been approached from the south on a track leading across the plain of Petra, around Jabal Haroun ("Aaron's Mountain"), the location of the Tomb of Aaron, said to be the burial-place of Aaron, brother of Moses. Another approach was possibly from the high plateau to the north. Today, most modern visitors approach the site from the east. The impressive eastern entrance leads steeply down through a dark, narrow gorge (in places only 3–4 m (9.8–13.1 ft) wide) called the Siq ("the shaft"), a natural geological feature formed from a deep split in the sandstone rocks and serving as a waterway flowing into Wadi Musa. At the end of the narrow gorge stands Petra's most elaborate ruin, Al Khazneh (popularly known as and meaning "the Treasury"), hewn into the sandstone cliff. While remaining in remarkably preserved condition, the face of the structure is marked by hundreds of bullet holes made by the local Bedouin tribes that hoped to dislodge riches that were once rumored to be hidden within it.
A little further from the Treasury, at the foot of the mountain called en-Nejr, is a massive theatre, positioned so as to bring the greatest number of tombs within view. At the point where the valley opens out into the plain, the site of the city is revealed with striking effect. The amphitheatre has been cut into the hillside and into several of the tombs during its construction. Rectangular gaps in the seating are still visible. Almost enclosing it on three sides are rose-colored mountain walls, divided into groups by deep fissures and lined with knobs cut from the rock in the form of towers.