A flint-mining hill fort dating to 250 BC

Cissbury Ring, a 208-acre Site of Special Scientific Interest in West Sussex, is England’s second largest hill fort and features one of the UK’s first known flint mines. The site, owned by the National Trust, boasts 270 mining shafts, up to 12 metres deep, carved into Cissbury Hill over 300 years. The Neolithic flint mine was developed around the beginning of the Middle Iron-Age, likely around 250 BC. Approximately eight interconnected galleries run from the bottoms of these shafts, witnessing the transition from open-cast to deep-shaft mining. The hill fort also encompasses a defensive wall, lined with a timber palisade, which has been damaged by illicit metal detecting.

Sources: Wikipedia, OpenStreetMap, Wikidata, Wikimedia Commons