Berkhamsted Castle is a good example of a motte and bailey castle where the original wooden defences were later rebuilt in stone. It consists of a large bailey, with parts of its curtain wall still standing, and a motte to one side, on which there are traces of a stone tower. The entire castle is surrounded by two moats, separated by an earth rampart.

The castle was built in the late 11th century for Robert of Mortain, William the Conqueror's half brother. Between 1155-65, Thomas a Becket, Henry II's chancellor, was resident at the castle. During this time he replaced the wooden palisades around the motte and bailey with new stone defences. Further improvements were made by King John, who added wing walls up the south side of the motte, and round towers along the bailey curtain wall. These defences were put to the test in 1216 when the castle was besieged by Prince Louis of France, as part of an attempt to seize the English Throne. The castle finally fell after a two week barrage from giant catapults called mangonels.

Later residents also made modifications to the castle, including Richard, Duke of Cornwall, who is thought to have added a three-storeyed tower along the western part of the curtain wall. The castle became disused from 1495. The outer gate or barbican was lost in 1838 when the London and Birmingham Railway sliced off the south-western edge of the site.