The irregular trace of the Citadel sprawls across the gently domed top of the Heights, its longer axis aligned north-west to south-east. The earthwork rampart and ditch were completed by 1806 and the brick revetment was added and completed by 1809. The ditch surrounding the main fort may be divided into four sections: the North Ditch; The Gorge Ditch (on the eastern side); the Inner South Ditch and the West Ditch. The zigzag western side owes its outline to the late 18th-century engineers but was remodelled in the early 19th, while the North-West Bastion, the tenaille on the south and the gorge on the east are purely a product of the early 19th-century. The North-West Bastion projects some way downhill along a natural spur in order to provide flanking fire east and west along the slope of the Heights, while the remains of the tenaille draw a hard straight line along the crest of the ridge on the south. The junctions of the Citadel ditch with the ditches of the North Lines and the South Lines are extant, although in the latter case this comprises only the scarp revetment.

The scarp and counterscarp revetments of the main ditch are were built in stock brick, steeply battered and usually strengthened at the salient angles with large dressed stone quoins. The general bond pattern is that of Flemish bond to between ½ and ¾ height, with English above but in a couple of locations the bond is all English or Flemish. Despite this, it seems that the Napoleonic work is in Flemish bond while that of the 1850s/60s is in English bond and represents a deliberate heightening.

The revetments define a flat-bottomed ditch, on average 9.1m wide at base and around 6.5m high. The base is either level or cut to an even incline, depending upon the ground to be negotiated, and generally survives to its original depth. The gorge ditch is cut at a higher level than the rest, leaving steep drops at its north and south ends. (1)

A plan dating to 1811 shows the new Napoleonic works on the fort, including the new layout of the ditch (2)

<1> English Heritage, 2004, The Western Heights, Dover, Kent: Report No. 2: The Citadel (Unpublished document). SKE17690.

<2> Major W H Ford, Royal Engineers, 1811, Plan Shewing the Appropriation of the Ordnance Lands on the Western Heights Dover 1811 (Map). SKE51523.