Hundreds of miles south of modern Tripoli, the fertile oasis of Wadi el-Agial stretches across the Libyan desert. A narrow, winding valley wedged between a great sand sea to the north and a clifflike rock escarpment to the south, the wadi seems an unlikely site for the capital of a lost civilization. Between the first and fourth centuries A.D., however, this oasis lay at the heart of the great Garamantian empire. Ruling from their capital city of Germa, the Garamantes once controlled more than 100,000 square miles of Africa (compare with photo of city of Germa landscape).