Scarborough Castle covers a large acreage, including the entire top of the headland
and stretching beyond in the form of a barbican. The headland is a naturally defensible place: high cliffs drop into the sea all the way from the north-north-west around the east and to the south; on the northwest and southwest is a steep hill; and also there is a natural freshwater spring near the eastern edge. (See map below.) By the early 13th century, man-made fortifications had made this headland almost impenetrable, until the invention of powerful cannons.
The seaward-facing eastern and northern edges of the headland may well have had fortifications, but they were probably simple - maybe originally a timber palisade and later a low stone wall. More elaborate defenses were not needed, because the rather loose but nearly vertical cliff would be extremely difficult to climb and anyone pushed away at the top would fall to his death. What eastern walls existed, however, have long since fallen into the ocean as the cliffside is slowly crumbled back by wind and water.
At the extreme western end of the castle the current barbican, rebuilt in the 14th century, is the most recent large addition to the castle defenses. It is toward the town, and on the northwest end, of the castle dike. The barbican, or first ward, is the first level of defense. Castle Road, running up from the town, ends at the main gate which is flanked by two massive half-round towers.
Author: Claudia J. Richardson
Article and Image Source: http://kinemage.biochem.duke.edu/panther/scarborough/index.scar.html
Keywords: Scarborough, Castle, Structure, History, UK