الربع الخالي
South and west of Abu Dhabi, vast, rolling sand dunes merge into the Rub' al Khali (Empty Quarter) of Saudi Arabia. The desert area of Abu Dhabi includes two important oases with adequate underground water for permanent settlements and cultivation. The extensive Liwa Oasis is in the south near the undefined border with Saudi Arabia, and about to the northeast is Al Buraymi Oasis, which extends on both sides of the Abu Dhabi-Oman border.