Saudi Arabia is, for the most part, an uninhabited desert land, which includes the Rub' Al Khali Desert, the larges mass of sand in the world, and the An-Nafud Desert - where sand dunes often exceed 100 ft. in height.
The land (desert) rises into hills and mountains in the west and southwest, along the edges of the Red Sea. Mountain ranges include the Hejaz in the northwest, and the Azir in the southwest.
Saudi Arabi's highest point is Jabal Sawda' which peaks at 10,279 ft. (3,133 m).
There are no perennial lakes or rivers.