In the west, however, there are mountain ranges running the full length of the Red Sea. Most of it consists of massive rolling sand dunes, but to the west there are gravel plains that rise towards the mountains of the Asir, and to the east there are salt pans, near the Arabian Gulf.
Oases are few, and movement has always been difficult.
Oil has been found in its northeastern corner. There are people who live in the oases deep in the desert that is known as the Rub' Al-Khali, or Empty Quarter, which is the largest continuous stretch of sand in the world, extending for about 248,000 square miles in the southeastern part of the country. Today, on the immense sand dunes you might find not only nomads with camels, but all-terrain vehicles with engineers looking for oil and archaeologists searching for ancient sites. Riyadh was originally a small settlement beside a wadi, or seasonal stream, feeding an oasis of date palms. Although the city has spread out into the surrounding desert, and is now home to some three million people, the name is still apt, since there are many parks and green areas, watered by means of modern technology.