kitchen tower, virtually a tower house in its own right, is . The vaulted kitchen is on the hall level, above a cellar. One of the best-appointed castle kitchens in Scotland of its date, it has an oven and a fireplace. A stair turret, added in 1581 and possibly replacing a timber stair, leads up from the lobby to two storeys of guest rooms. These include the "Royal Apartments", a suite of two bedrooms plus an audience chamber, suitable for royal visitors. Courtyard and curtain wall Projecting stones on the south wall of the kitchen block, known as tuskings, and four pointed-arched windows in the south curtain wall, suggest that further ranges of buildings were planned. The large, easternmost window, may have been intended for a chapel, and it is recorded that a chapel dedicated to the 8th-century monk Saint Fillan was located at Doune Castle, but the lack of foundations suggest that there was no large building in this part of the castle. The foundations which do exist were excavated in September 2002, revealing a structure which was interpreted as a kiln or oven against the south wall. The central well is around deep. The curtain wall is thick, and high. A walkway along the top of the wall is protected by parapets on both sides, and is carried over the pitched roofs of the hall and gatehouse by steep steps. Open, round turrets are located at each corner, with semicircular projections at the midpoint of each wall. A square turret with machicolations is located above the postern gate in the west wall. Interpretation of the layout The Lord's tower is a secure, private set of rooms, probably intended for the sole use of the Lord and his family, and with its own lines of defence. The architectural historian W. Douglas Simpson interpreted this arrangement as being the product of the "bastard feudalism" of the 14th century. During this period, Lords were required to defend their castles by means of mercenaries, rather than the vassals of the earlier feudal system, and Simpson suggested that the Lord of Doune designed his tower to be defensible against his own, potentially rebellious, garrison. This interpretation is no longer widely accepted by historians, and the castle is instead seen as a development towards more integrated courtyard buildings, such as the royal palace of Linlithgow, which was constructed through the 15th and early 16th