Maumbury Rings is a Neolithic henge in the south of Dorchester town in Dorset, England (grid reference SY690899). It is a large circular earthwork, 85 metres in diameter, with a single bank and an entrance to the north east. It was modified during the Roman period when it was adapted for use as an amphitheatre, and the site was remodelled again during the English Civil War when it was used as an artillery fort guarding the southern approach to Dorchester.