The remains of Castle Acre Castle are located in the southern part of the modern village of Castle Acre, Norfolk. They include a roughly circular inner bailey with an adjoining outer bailey to the south east and a triangular barbican to the east.
The inner bailey is surrounded by a ditch and an inner bank surmounted by a curtain wall, and contains the ruins of a large stone building. The outer bailey is also surrounded by a ditch, with internal banks on the east and west sides, and fragmentary remains of a wall crowning the banks and closing the southern end. The first stone building constructed in the centre of the inner bailey was a two-storey residential building, built between 1070 and 1085. Originally, it stood in the centre of a courtyard surrounded by a ditch and bank which survives as a buried feature beneath the later earthworks. In around 1140 the house was converted to a keep. The associated strengthening of the surrounding defences included the enlargement of the ditch, the raising of the bank and the construction of a curtain wall. A second period of development at the castle saw the area of the keep halved and the perimeter defences of the inner bailey strengthened yet again. The perimeter bank was heightened and on top of the existing curtain wall, was built a second curtain of solid flint. An eastern and western gatehouse provided entry to the outer bailey. The foundations of three buildings are located within the outer bailey and are thought to have been a great hall, detached kitchen and a chapel. The hall was thought to have replaced the house in the inner bailey, after its conversion to a keep.
Throughout the 12th and 13th centuries the castle continued to be an important administrative centre, but by 1397 it was derelict. The estate was eventually acquired by Sir Edward Coke in 1615, in whose family it remains. The castle was taken into state guardianship in 1929 and is currently opened to the public by English Heritage (2009).