towers as their means can provide. Inside the enclosure is a citadel, or keep, which commands the whole circuit of the defences. The entrance to the fortress is by means of a bridge, which, rising from the outer side of the moat and supported on posts as it ascends, reches to the top of the mound." At Durham Castle, contemporaries described how the keep arose from the "tumulus of rising earth" with a keep reaching "into thin air, strong within and without", a "stalwart house...glittering with beauty in every part". As well as having defensive value, keeps and mottes sent a powerful political message to the local population. Wooden keeps could be quite extensive in size and, as Robert Higham and Philip Barker have noted, it was possible to build "...very tall and massive structures." As an example of what these keeps may have comprised, the early 12th-century chronicler Lambert of Ardres described the wooden keep on top of the motte at the castle of Ardres, where the "...first storey was on the surface of the ground, where were cellars and granaries, and great boxes, tuns, casks, and other domestic utensils. In the storey above were the dwelling and common living-rooms of the residents in which were the larders, the rooms of the bakers and butlers, and the great chamber in which the lord and his wife slept...In the upper storey of the house were garret rooms...In this storey also the watchmen and the servants appointed to keep the house took their sleep." In the Holy Roman Empire, tall, free-standing, wooden (later stone), fighting towers called Bergfriede were commonly built by the 11th century, either as part of motte-and-bailey designs or, as part of Hohenburgen castles, with characteristic inner and outer courts. Bergfriede, which take their name from the German for a belfry, had similarities to keeps, but are usually distinguished from them on account of Bergfriede having a smaller area or footprint, usually being non-residential and being typically integrated into the outer defences of a castle, rather than being a safe refuge of last resort. Early stone keeps (10th–12th centuries) During the 10th century, a small number of stone keeps began to be built in France, such at the Château de Langeais: in the 11th century, their numbers increased as the style spread through Normandy across the rest of France and into England, South Italy and Sicily. Some existing