mountainous area, northwestern Saudi Arabia, bounded by the regions of Hejaz on the west and Ash-Sharqīyah on the east. The principal features of the region are the two great mountain ranges of Ajāʾ (granites) and Salmā (basalts) and the immense rolling sand dunes of An-Nafūd. The oasis town of Ḥāʾil is situated on the southern flank of the Ajāʾ, while an older capital, Fayd, lies in the midst of Salmā. Both towns were important stations on the pilgrim route to Medina from Iraq and Iran (Persia). But in modern times this traffic (by motor vehicle) is negligible, because the pilgrims prefer the amenities of Riyadh, which is accessible by air and by rail.