Rochester Castle, which includes a tower keep, a bailey with a curtain wall and an outer ditch, dominates the point where the Roman Watling Street - originally the main road between Canterbury and London - crosses the River Medway. Although the castle dates from the immediate post-Conquest period and has a well-documented history from its foundation onwards, the earliest occupation of the site is likely to have been in the Roman period. The western curtain wall overlies an earlier Roman wall at this point, making it likely that the area of the castle was once within the Roman town of Durobreve. The earliest references to the castle are in Domesday Book - where it is recorded that the Bishop of Rochester had been given land in Aylesford `in exchange for land on which the castle stands' - and in the Textus Roffensis, where the land on which the castle was built is said to be `the best part of the city'. The first fortification of the site in stone is generally accredited to Bishop Gundulf after the siege of 1088. The wording of the agreement for work to be carried out also implies that an earlier castle, not built of stone, originally occupied the site, although no trace of this structure has yet been identified. The four-storeyed stone keep, one of the largest in England, is 21m square with walls up to 3.5m thick and 34.5m high to the top of the parapet. The south east corner of the keep has been rebuilt, probably as a result of the breaching during the siege of 1215. To the north of the keep, an irregular bailey, some 120m from north to south, is ow partly defined by the curtain wall which once enclosed it; this survives on the west side of the bailey where it is all that can be seen of the Gundulfian period of construction. This section was built on top of the foundations of the Roman city wall and was subsequently altered in the 13th century. A long section of the curtain wall on the south side of the castle was demolished in modern times, but at the east end a section of wall with drum towers (the work of Henry III) survives. Beyond the curtain wall on the landward side, but only now visible to the east and north of the castle itself, are the remains of the castle ditch. Although this has been partly infilled and built on over the years, it still survives as a relatively deep buried feature. Below the levels of modern disturbance, deposits will survive providing evidence for the occupation of the site and the environment and economy of the surrounding area. It has been suggested that a second bailey existed immediately to the south west of the keep. However there is currently no confirmation of this and the area is not included in the scheduling. In 1127 Henry I gave the custody of Rochester Castle to the Archbishop of Canterbury and his successors, and shortly after this Archbishop William de Corbeuil began the construction of a stone keep in the southern part of the bailey. Various repairs to the castle and town defences are recorded in the Pipe Rolls for 1166-1167, 1170-1171 and the castle itself was strengthened during the reign of Richard I (1189-1199). During the siege of 1215, the curtain wall and the south east corner of the keep were undermined by King John's engineers, and the castle eventually fell to the besiegers. Subsequently, urgent repairs were made to the keep and the curtain wall, with the tower on the south east angle being rebuilt between 1221 and 1222 on a circular plan, thereby making it much more difficult to undermine. In 1237 mention is made of a southern gateway to the castle wall and the construction of a drawbridge - no trace of which can now be seen. In 1264 the castle was subjected to another siege, when Earl Warrene and Roger de Leybourne held it for the king against Simon de Montfort and Gilbert de Clare. The barons breached the city wall and the outer defences of the castle, but the great keep held out and they were eventually forced to withdraw. Little effort was made to repair the damage caused by this onslaught, and in the 1340 survey made for Edward III, it was reported that there were `dilapidations over the whole extent of the castle'. Thus in 1367 a programme of rebuilding was begun. Of the two mural towers to the south of the main gate on the east of the castle, the northernmost was built new at this time and the southern one was rebuilt. By 1370 the programme was complete. Between 1378 and 1383, a new tower was built on the north angle of the curtainwall. Further demolitions and alterations are known to have taken place c.1872. The keep and curtain wall are Listed Grade I, and are included in the scheduling as is the ground beneath them. All modern features within the bailey are excluded: these include: rubbish bins, lamp posts, the bandstand, the two lavatory blocks to the north east of the keep, the kiosk at the north of the bailey, the iron railings flanking the steps down to the Esplanade, the steps themselves and their associated Victorian gates (which are Listed Grade II), the surfaces of all paths, the modern wooden stairs leading into the keep and all modern features within the keep (the flagpole, wooden platforms, handrails, metal window bars, perspex panels in the window openings, the modern protective roof, the metal grille in the south west turret, all electrical fittings and cables and all the modern additions in the English Heritage shop in the forebuilding); similarly, all modern features within The Lodge are excluded, although the ground beneath all these features is included within the scheduling. Outside the bailey in the castle ditch, the surface of all car parks, roads and paths, lamp posts, rubbish bins, all modern walling and railings are excluded from the scheduling, although the ground beneath these features is included.