The main concern of the baron who was contemplating the construction of a castle was to ensure that he could hold out against a besieging force for as long as possible. Though the design of a castle was certainly an important factor, equally important was its location. The ideal site for a castle was atop an existing hill. Not only did this vantage point give the garrison a clear view of all approaches to the castle, it would effectively slow down an attacking force if it had to climb uphill. The site could not be too inaccessible, of course. The defenders had to be able to exit the castle readily, either to make a counterattack or, if all else failed, to make their escape.

Another favorite location was next to a river, preferably in a spot where the river formed a large...