Ditch (fortification) in the context of "Old Sarum"

Maiden Castle is an Iron Age hillfort 1.6 mi (2.6 km) southwest of Dorchester, in the English county of Dorset. Hill forts were fortified hill-top settlements constructed across Britain during the Iron Age. The earliest archaeological evidence of human activity on the site consists of a Neolithic causewayed enclosure and bank barrow. In about 1800 BC, during the Bronze Age, the site was used for growing crops before being abandoned. Maiden Castle itself was built in about 600 BC; the early phase was a simple and unremarkable site, similar to many other hill forts in Britain and covering 6.4 ha (16 acres).

Around 450 BC it was greatly expanded and the enclosed area nearly tripled in size to 19 ha (47 acres), making it the largest hill fort in Britain and, by some definitions, the largest in Europe. At the same time, Maiden Castle's defences were made more complex with the addition of further ramparts and ditches. Around 100 BC, habitation at the hill fort went into decline and became concentrated at the eastern end of the site. It was occupied until at least the Roman period, by which time it was in the territory of the Durotriges, a Celtic tribe.

A moat is a deep, broad ditch dug around a castle, fortification, building, or town, historically to provide it with a preliminary line of defence. Moats can be dry or filled with water. In some places, moats evolved into more extensive water defences, including natural or artificial lakes, dams and sluices. In older fortifications, such as hillforts, they are usually referred to simply as ditches, although the function is similar. In later periods, moats or water defences may be largely ornamental. They could also act as a sewer.

A scarp and a counterscarp are the inner and outer sides, respectively, of a ditch or moat used in fortifications. Attackers (if they have not bridged the ditch) must descend the counterscarp and ascend the scarp. In permanent fortifications, the scarp and counterscarp may be encased in stone. In less permanent fortifications, the counterscarp may be lined with paling fence set at an angle so as to give no cover to the attackers, but to make advancing and retreating more difficult.

If an attacker succeeds in breaching a wall, a coupure can be dug on the inside of the wall to hinder the forlorn hope, in which case the side of the ditch furthest from the breached wall and closest to the centre of the fortification is also called the counterscarp.

An outwork is a minor fortification built or established outside the principal fortification limits, detached or semidetached. Outworks such as ravelins, lunettes (demilunes), flèches and caponiers to shield bastions and fortification curtains from direct battery were developed in the 16th century. Later, the increasing scale of warfare and the greater resources available to the besieger accelerated this development, and systems of outworks grew increasingly elaborate and sprawling as a means of slowing the attacker's progress and making it more costly. When taken by an enemy force, their lack of rear-facing ramparts left them totally open to fire from the main works.

An advanced work, a fortification detached and forward of the main castle or fortification, is sometimes referred to as a type of outwork or 'advanced outwork'.

A fence is a structure that encloses an area, typically outdoors creating a boundary, and is usually constructed from posts that are connected by boards, wire, rails or netting. A fence differs from a wall in not having a solid foundation along its whole length.

Alternatives to fencing include a ditch (sometimes filled with water, forming a moat).

A burgus (Latin, plural burgi ) or turris ("tower") is a small tower-like castrum of late antiquity, which was sometimes protected by an outwork and surrounding ditches. Timothy Darvill defines it as "a small fortified position or watchtower usually controlling a main routeway."

Burgus was a term used in the later period of the Roman Empire, and particularly in the Germanic provinces.

A ringwork is a form of fortified defensive structure, usually circular or oval in shape. Ringworks are essentially motte-and-bailey castles without the motte. Defences were usually earthworks in the form of a ditch and bank surrounding the site.

Ringworks originated in Germany in the 10th century as an early form of medieval castle and at first were little more than a fortified manor house. They appeared in England just prior to the Norman conquest and large numbers were built during the late 11th and early 12th centuries. More elaborate versions (such as Stansted Mountfitchet Castle) comprise a ringwork and bailey, the ringwork replacing the more usual motte and the bailey acting as a military stronghold.