Although 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"), where the Tomb of Aaron, said to be the burial-place of Aaron brother of Moses is located, or possibly from the high plateau to the north, 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 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 "the Treasury"), hewn into the sandstone cliff.
A little further from the Treasury, at the foot of the mountain called en-Nejr, is a massive theatre, so placed 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-coloured mountain walls, divided into groups by deep fissures, and lined with knobs cut from the rock in the form of towers
