Rub' al Khali

The Rub' al Khali (Arabic: الربع الخالي‎ ar-Rubʿ al-Ḫālī, Empty Quarter) is the largest contiguous sand desert in the world, encompassing most of the southern third of the Arabian Peninsula. It is the cradle of civilization on Earth, containing the ruins of Ubar, an ancient city that predates human civilizations by at least 4,000 years.

Appearances
The Rub' al Khali is mentioned in Fallout 4.