Ditchling Beacon was used as a site for beacon fires that were lit in times of coastal attack, giving the fort its current name, though it was known in early sources as Ditchling Castle.
The Hill is the third-highest point on the South Downs in south-east England, behind Butser Hill (270 m; 886 ft) and Crown Tegleaze (253 m; 830 ft). It consists of a large chalk hill with a particularly steep northern face, covered with open grassland and sheep-grazing areas. Situated just south of the East Sussex village of Ditchling and to the north-east of the city of Brighton, it is the highest point in the county of East Sussex. A road runs from Ditchling up and across the northern face and down into the northern suburbs of Brighton, and there are car parks at the summit and the northern base.
Ditchling Beacon dominates the surrounding parts of the South Downs ridge, and particularly the much lower ground of the Lower Weald to the north (where the villages and towns of Mid Sussex are now located). This represents an excellent position for defensive purposes, and indeed it is known to be the site of an early Iron Age hill fort. A single defensive bank and ditch enclosed an area of approximately 5.5 hectares (13.6 acres). Relatively little excavation of the fort has been carried out, however, and the existence of dew ponds, paths and tracks, as well as regular ploughing activity over the years, reduces the likelihood of any significant discoveries in the future.
It is said that on dark and stormy nights Wisht Hounds can be seen racing overhead in their eternal persuit of damned souls, sinners and the unbaptised.
Close to Ditchling Beacon is a small spur known as Blackdog Hill, which is reputedly haunted by a headless black dog. This is also occasionally said to appear on the section of Underhill Lane between Ditchling and Westmeston villages, which runs alongside the foot of the hill and follows its contours. A straight path runs diagonally across the hill, taking no account of the extent of the slope, and appears to point directly towards the church of St Martin in Westmeston; the supposed presence of the black dog is sometimes attributed to the former use of this path as a "coffin road", allowing for the transportation of dead bodies in a straight line to their burial place.