Tuwaiq

Jabal Tuwaiq () or Tuwaiq Escarpment is a narrow escarpment that cuts through the plateau of Najd in central Arabia, running approximately from the southern border of Al-Qasim in the north, to the northern edge of the Rub' al Khali desert near Wadi ad-Dawasir in the south. It is high and also has a Middle Jurassic stratigraphic section. The eastern side slopes downwards gradually, while the western side ends in an abrupt manner. The escarpment can be thought of as a narrow plateau, though the locals refer to it as a jebel ("mountain"). Marshall Cavendish used the name "Tuwayr Mountains" to describe mountains of central Arabia, distinct from the Shammar in the north, the Dhofar in the south, and the Hajar to the east.

Many narrow valleys (wadis) run along its sides, such as Wadi Hanifa, and a group of towns lie on its central section, including the Saudi capital, Riyadh. Many settlements have historically existed on either side of it as well, such as those of Sudair and Al-Washm. The Tweig escarpment is mentioned in Yaqut's 13th century geographical encyclopedia under the name "Al-'Aridh", though for the past few centuries that name has applied only to the central section of it, around Riyadh.