Cissbury Ring is an 84.2-hectare (208-acre) biological Site of Special Scientific Interest north of Worthing in West Sussex. It is owned by the National Trust and is designated a Scheduled monument for its Neolithic flint mine and Iron Age hillfort. Cissbury Ring is the largest hill fort in Sussex, the second largest in England and one of the largest in Europe overall, covering some 60 acres (24 hectares). The earthworks that form the fortifications were built around the beginning of the Middle Iron-Age possibly around 250 BC but abandoned in the period 50 BC - 50 AD.