A coastal artillery battery on the cliff at the southern end of Harwich, with gun emplacements, magazines, and observation posts spread across the headland between the town and Dovercourt. The site has been fortified since 1543 but the present concrete structures are late-Victorian and Second World War, when Harwich was a major naval base and the battery's six-inch guns were part of the defences against German U-boats in the North Sea.
The site is open to walkers as part of a long coastal footpath. The Harwich Society has restored several of the buildings and opens them on occasional summer weekends. The clifftop view across the estuary towards Felixstowe and the open sea is the second-best in town, after the top of the Redoubt.