The castle is in the form of a hollow square, with bold round towers at each corner, and central to each side rising from a battered plinth. The barbican is on the N side, between the NE tower and the centre tower, approached by a ramped bridge, a pointed arch of 2 chamfered orders. C19 ashlar parapet with ridged copings. The barbican itself has a tall outer arch, and within, an inner arch of 2 orders behind the portcullis drop. The mantled and supported Myddleton Arms, by A W Pugin, are set in a recess over. Two levels of small side arrowslits. Studded framed doors. Within the entrance, C19 doors with pointed arches each side and a timber joisted ceiling. The inner doors are set in another arch of 2 chamfered orders, on one the inscribed date 1669 TM. The doors are framed and set inside the arch.
The main towers are of 3 storeys, with stone mullioned and transomed windows and crenellated parapets added in the C19 after the upper stages of the towers had been demolished in 1659, and the C18 balustrade removed. In the plain stone curtain between the towers, a series of irregularly placed similar stone windows, some with horizontal hood moulds. The W elevation is similar, with similar windows, the crenels of the parapet partly blocked. A dog-leg external stair rises to a doorway, and further S, the base of a garderobe chute. Beyond the centre tower, the castle was demolished, the curtain stopping at an irregular break, now built up in the C14 in rubble as part of the rebuild of the S side, and continued further in the C19 to join the stables.
The S elevation is largely obscured for much of its length by the C18 and C19 stables and workshop additions, but beyond the W privy garden wall, the C14 character is apparent in the two 2-light transomed and cusped windows to the chapel and a further trefoil light to the left. Other windows of the C19. Two gabled buttresses.
The E elevation has a fine 5-light window to the chapel S of the central tower, created by Sir Arthur Blomfield in 1894 to replace one by E W Pugin, the wall deeply battered below. The curtain between the centre and the NE tower has similar stone mullioned and transomed windows with label heads, also repeated on the towers. Crenellated parapet.
Courtyard elevations: The W side is still largely medieval, of c1300, although the upper part of the N end is rebuilt. Low 2-centred door to the Guard Room, and adjacent, a trefoil-headed door. Above, bracketed out on corbels, a bellcote of 1609, refurbished by E W Pugin, and now with a clockface of 1960 over a 2-light window. Bell stage has 2 x 1 shoulded open arches and a hipped lead roof. To the left, the medieval Adam tower, crenellated with spiked coping to the merlins. Other windows mostly 3-light mullioned and transomed.
The S side is of 1529, 3-storey, with mullioned and transomed windows and doors with depressed arches. The imprint of 9 gables from the C17 roofs is visible, replaced in the C18 when the wall was taken up to a level parapet. Two light attic windows. The door to the Chapel, at the E end has a segmental pediment containing a large weathered winged putto.
The E side is of 1664-1678, a 2-storey range with 7 mullioned and transomed 3-light windows and parapet over, against which is built a single storey range by E W Pugin in c1846, buttressed between windows and a central porch with a crenellated parapet. Arms over the door.
The N side is of c1630-40 with later alterations. Irregularly placed mullioned and transomed windows. A 2-centred chamfered arch to the kitchen has an inscription over
THIS:NEW:BUILDING:/AND:THE:TOURE:WAS:BU/ILT:ALL:IN:ONE:YEARE:BY:TH/ OM MYDDLETON KNIGHT 1636. To the right, steps to a door by Pugin dated 1846.