Saudi Arabia is dry. It has no permanent rivers anywhere in the country though there are many "Wadi" that fill with water when it rains. In spite of this dryness, Saudi Arabia has a surprisingly varied terrain and supports a large variety of hearty desert and mountain plants.

As most people expect, much of Saudi Arabia is covered with sand deserts. The largest sand desert in the world in located in Saudi Arabia's southern portion. It is a region appropriately called "The Empty Quarter" or "Ar Rub Al-Khali." The Ar Rub Al-Khali contains sand dunes that are hundreds of miles long and can be up to 500 feet tall. These sand dunes form natural "corridors" in the desert. Much of the rest of Saudi Arabia is covered with a rocky type of desert similar to that found in the Sahara desert of northern Africa.

The western region of Saudi Arabia close to the Red Sea and south of Jeddah is mountainous and supports the country's only natural farmland. But even this region is dry and must be irrigated in order to support farming. In many areas the abundant rocks have been used to create farming terraces. Fortunately, modern farming techniques and irrigation have helped Saudi Arabia create successful farming regions that would not be possible naturally. The Asir region contains spectacular mountain vistas and cliffs.