The Cyrenaica was the region in North Africa located between Roman Egypt and Tripolitania; today it is part of Libya. It is cut off to the north and west by the Mediterranean and to the east and south by the Sahara desert. The main city, Cyrene, was founded by Greek settlers from Thera in the seventh century bce. Around 320 bce the region came under the control of the Ptolemies, who ruled it almost continuously until the first century bce, when it was taken over by the Romans.