Curtain wall (fortification)

[3] In medieval castles, the area surrounded by a curtain wall, with or without towers, is known as the bailey.

In medieval designs of castle and town, the curtain walls were often built to a considerable height and were fronted by a ditch or moat to make assault difficult.

Walls were topped with battlements which consisted of a parapet, which was generally crenellated with merlons to protect the defenders and lower crenels or embrasures which allowed them to shoot from behind cover; merlons were sometimes pierced by loopholes or arrowslits for better protection.

Behind the parapet was a wall walk from which the defenders could fight or move from one part of the castle to another.

[5] The introduction of gunpowder made tall castle walls vulnerable to fire from heavy cannon, which prompted the trace italienne style from the 16th century.

Beaumaris Castle in Anglesey in North Wales , with curtain walls between the lower outer towers, and higher inner curtain walls between the higher inner towers.
Reconstruction of the 9th-century BC defensive walls around ancient Tel Lachish in modern Israel .
The 12th-century curtain wall of the Château de Fougères in Brittany in northern France, showing the battlements, arrowslits and overhanging machicolations .
Two sections of the 16th-century curtain wall around Berwick-upon-Tweed , at the eastern end of the Anglo-Scottish border .