Draa Valley was part of the Caesar in Africa series designed by Dragon2. There were supposed to be 10 levels in this series, but only 5 were finished (AFAIK). Just design-wise, this was the most accomplished of the released scenarios.
Story (by the original author)
To the south of the Atlas mountains the Draa river flows into the Sahara Desert, creating a long oasis through an otherwise desolate land. It is here that the Empire will establish a major city before venturing south across the desert.
The Emperor has acquired a taste for the dates that grow along the river and will require large shipments once your city is established. The patricians of Rome, copying the tastes of the Emperor as always, have been bidding up the price of Draa valley fruit, and it may become a profitable export for you. The locally-produced weapons, in contrast, have acquired a poor reputation.
The Egyptians, who were content with us as fellow colonizers while we remained north of the Atlas mountains, now appear ready to challenge us. Our troops can keep the road to Rome secure, but you had better be prepared for attacks out of the desert from almost any direction. The rugged terrain outside the river valley, useless for habitation, appears ideal for defense.