 In the Neolithic period, the South Downs above Worthing was one of Britain's largest and most important flint-mining centres.These extensive flint mines which include the considerable mines at Cissbury are in many ways comparable to the vast flint mines of Spiennes in Belgium which have been given World Heritage Site status.The secondary southern escarpment of the South Downs close to Worthing, south of the main ridge of the Downs (formed by hills such as Steep Down, Cissbury, Church Hill and Harrow Hill) is most visible west of the River Adur and it is this flint which is especially hard and durable and hence valuable in Neolithic times.