<P> An urban civilization, the Garamantes, arose around 500 BCE in the heart of the Sahara, in a valley that is now called the Wadi al - Ajal in Fezzan, Libya . The Garamantes achieved this development by digging tunnels far into the mountains flanking the valley to tap fossil water and bring it to their fields . The Garamantes grew populous and strong, conquering their neighbors and capturing many slaves (who were put to work extending the tunnels). The ancient Greeks and the Romans knew of the Garamantes and regarded them as uncivilized nomads . However, they traded with them, and a Roman bath has been found in the Garamantes' capital of Garama . Archaeologists have found eight major towns and many other important settlements in the Garamantes' territory . The Garamantes' civilization eventually collapsed after they had depleted available water in the aquifers and could no longer sustain the effort to extend the tunnels further into the mountains . </P> <P> The Berber people occupied (and still occupy) much of the Sahara . The Garamantes Berbers built a prosperous empire in the heart of the desert . The Tuareg nomads continue to inhabit and move across wide Sahara surfaces to the present day . </P> <P> The Byzantine Empire ruled the northern shores of the Sahara from the 5th to the 7th centuries . After the Muslim conquest of Arabia, specifically the Arabian peninsula, the Muslim conquest of North Africa began in the mid-7th to early 8th centuries and Islamic influence expanded rapidly on the Sahara . By the end of 641 all of Egypt was in Muslim hands . Trade across the desert intensified, and a significant slave trade crossed the desert . It has been estimated that from the 10th to 19th centuries some 6,000 to 7,000 slaves were transported north each year . </P> <P> In the 16th century the northern fringe of the Sahara, such as coastal regencies in present - day Algeria and Tunisia, as well as some parts of present - day Libya, together with the semi-autonomous kingdom of Egypt, were occupied by the Ottoman Empire . From 1517 Egypt was a valued part of the Ottoman Empire, ownership of which provided the Ottomans with control over the Nile Valley, the east Mediterranean and North Africa . The benefit of the Ottoman Empire was the freedom of movement for citizens and goods . Traders exploited the Ottoman land routes to handle the spices, gold and silk from the East, manufactured goods from Europe, and the slave and gold traffic from Africa . Arabic continued as the local language and Islamic culture was much reinforced . The Sahel and southern Sahara regions were home to several independent states or to roaming Tuareg clans . </P>

How long has the sahara been a desert