A spur castle is a type of medieval fortification that is sited on a spur of a hill or mountain for defensive purposes. Ideally, it would be protected on three sides by steep hillsides; the only vulnerable side being that where the spur joins the hill from which it projects. By contrast, a ridge castle is only protected by steep terrain on two sides.

Description

A spur castle was one of several types of hill castle. Depending on the local topography, a spur castle may have relied mainly on its inaccessible position or may have integrated further features such as shield walls and towers into the defences. In addition castle builders may have improved the natural defences of the terrain by hewing into them to make the hillsides harder to climb and reduce the risk of landslide. A classic feature is the neck ditch, cutting off the spur from the rest of the hill. A long spur castle is sometimes, but not always, subdivided into a lower ward and a more strongly defended upper ward (or even a succession of three or more wards). High spur and hilltop castles were built and improved by the Franks to hinder increasing use of the counterweight trebuchet. In the case of spur castles, heavy siege machinery could only be deployed on the uphill side enabling defensive works and forces to be concentrated there.

Examples