The castle is made up of an inner and an outer bailey, the former surrounded by a stone curtain wall defended by six mural or fortified towers and the castle keep. The inner bailey would have included a hall, solar, chapel and other service buildings of which only the foundations survive. The design of Conisbrough's keep is unique in England, and the historians Oliver Creighton and Stephen Johnson consider it an "architectural gem" and "one of the finest examples of late Norman defensive architecture". The keep comprises a circular central tower with six massive buttresses; its four floors would have included a main chamber and a private chamber for the lord above it. Although militarily weak, the design would have been a powerful symbol of Hamelin Plantagenet's new social status as a major lord.