The monument consists of Craigmillar Castle and its surrounding designed landscape. Craigmillar is arguably the best example of a medieval castle surviving in Scotland. Built according to 15th and 16th-century principles of fortification, it is instructively complete and picturesquely placed within the remains of a substantial and important designed landscape.
The core is the late 14th century L-shaped towerhouse built for the Preston family, the owners of the land from 1374 to 1660. The original entrance was in the re-entrant angle of the jamb. Facing W, it was protected by a shelving pitfall in the rocky crags. The towerhouse consists of the usual offices, with storage in the lower floor and its entresol, the great hall forming the first-floor of the main block and fitted with a late 15th-century fireplace. In the jamb adjacent to the hall was the kitchen, later adapted as a bedroom.
The massive enceinte was built in 1427, flush with the tower on the S and enclosing the present inner courtyard. It has rounded towers at each of the corners and a parapet walk to the N, E and part of the S. The NE tower forms one of the earliest artillery batteries in Scotland. Within the courtyard domestic accommodation was built against the E wall after the burning of the castle in 1544 by Hertford's army and against the W wall in 1661 when Sir John Gilmour, the new owner, added his fine renaissance house to complete the internal buildings.
The outer curtain or precinct wall was built soon after 1544 and was furnished with gunloops but not battlements. Within the precinct is a chapel of late 15th-century date. There were the usual farmyard offices, one of which is said to have been used later as a Presbyterian meeting place.
The field S of the castle has a pond shaped like a 'P', no doubt for Preston. This is the most visible remnant of the medieval garden to survive, but around it were probably more formal gardens and later an elaborate designed landscape with parkland and coppiced woodland. Beyond the wall around the field containing the 'P' pond is an area of quarrying associated with the building of the castle, later incorporated within the designed landscape, providing an area of coppiced woodland.
The area to be scheduled includes the castle and those elements of the designed landscape that can still be seen or inferred, and is marked in red on the attached map. The area measures a maximum of 1020m SW to NE by 830m NW to SE. All modern fences and roads are specifically excluded from the scheduling, but all masonry walls, including those at the boundaries of the scheduled area, are included.