from Wikipedia:

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.