The monument includes the known extent of the Benedictine Abbey of St Mary's situated in the town of West Malling. Much of the medieval abbey, which survives as upstanding masonry, has been incorporated into the post- Dissolution buildings which have been reused by, and purposely built for, the modern nunnery which began at the end of the 19th century. The upstanding medieval remains include the 14th-century gatehouse and chapel positioned on the north side of the precinct, the Norman tower, the 13th- century arcade of the south cloisters, the south wall and south transept of the church and various other upstanding remains of the east range comprising parts of the chapter house and dorter undercroft. These are situated in the northern part of the precinct which, when founded, covered an area of 4.8ha. In the southern part of the precinct is a medieval tithe barn converted in 1936-7 for use as a chapel. To the west of the main claustral complex lies the site of the 15th-century guest house. This is believed to have had an associated outer court of which no above-ground remains survive. Further buildings to the south include what are believed to be an infirmary or abbess's apartments, which survive as buried foundations. A stream runs from south to north through the precinct and feeds a fishpond to the south of the guest house. The nunnery was founded c.1090 by Gundulf, Bishop of Rochester. Two earlier dates for the foundation of an abbey at Malling have been put forward, 688 and 944, the latter by King Edmund, but neither has been proved. The land is known to have been in the possession of the Bishop of Rochester in 945 but was then lost to the Church and recovered by Lanfranc in 1076. The church was dedicated in 1106 but in 1190 the abbey and nearly all the town buildings were burnt down after which extensive rebuilding was undertaken. Dissolved in 1538 and granted to the Archbishop of Canterbury, the abbey later became the property of the Crown. In 1620 it was granted to John Rayney whose son sold it to the Honeywood family. During the 18th century the surviving ruins of the abbey were incorporated into a new house built mainly on the site of the south range. Partial excavation of the abbey was undertaken in the 1930s and in 1962 prior to the construction of the new church. The excavations at the east end of the medieval church showed that it had been square-ended, not apsidal as had previously been thought, with a rectangular chapel projecting from the centre of the east wall. All the medieval masonry is listed Grade I and the 18th-century cascade and the abbey barn are listed Grade II. Excluded from the scheduling are all the nunnery buildings presently in use which incorporate all of the listed medieval masonry (except for the tower which is included in the scheduling), all the other buildings within the precinct area, specifically the sheds, greenhouses, houses, barn, conventual buildings, the precinct wall and all other post-Dissolution walling, footbridges, fences and sundials; however, the ground beneath all these features is included except for the area of the present burial ground which is totally excluded from the scheduling. Reasons for Designation: A nunnery was a settlement built to sustain a community of religious women. Its main buildings were constructed to provide facilities for worship, accommodation and subsistence. The main elements are the church and domestic buildings arranged around a cloister. This central enclosure may be accompanied by an outer court and gatehouse, the whole bounded by a precinct wall, earthworks or moat. Outside the enclosure, fishponds, mills, field systems, stock enclosures and barns may occur. The earliest English nunneries were founded in the seventh century AD but most of these had fallen out of use by the ninth century. A small number of these were later refounded. The tenth century witnessed the foundation of some new houses but the majority of medieval nunneries were established from the late 11th century onwards. Nunneries were established by most of the major religious orders of the time, including the Benedictines, Cistercians, Augustinians, Franciscans and Dominicans. It is known from documentary sources that at least 153 nunneries existed in England, of which the precise locations of only around 100 sites are known. Few sites have been examined in detail and as a rare and poorly understood medieval monument type all examples exhibiting survival of archaeological remains are worthy of protection. Malling Abbey survives comparatively well and, despite damage caused by partial demolition and rebuilding, substantial sections of the medieval masonry are still upstanding. Partial excavation has shown that the foundations and layout of the other conventual buildings survive below ground level as buried features, with the site containing archaeological remains and environmental information relating to the construction and use of the abbey as well as the economy and way of life peculiar to a Benedictine nunnery.