In 1975-6, the Cambridge Archaeological Expedition made a preliminary survey of the Paleolithic sites in the Rohri Hills. According to their findings, the Rohri Hills were a source of chart for the manufacture of the parallel-sided blades used by the Harappan culture of 2300 - 1750 BC. The most clearly differentiated Paleolithic site in the Rohri Hills was at their southern end, near the village of Chancha Baloch and only four kilometers from the pre-Harappan settlement of Kot Diji. Spread over an area of about 5,000 square meters, on a largely sand- free area between the dunes, are found Middle and Upper Paleolithic artifacts and factory debris. An extensive series of working floors were also found close to a hamlet known as Nawab Punjabi. The discovery of factory sites representing all phases of the Stone Age in the lower Indus Valley has added more depth to our understanding of civilization in prehistoric Sindh.