The early Norman castle consisted, as a rule, of a single three-storied tower with walls of great thickness. But at a later period, after the experience gained in the Crusades, and in consequence of the introduction of powerful engines capable of throwing great stones against a besieged fortress, military architecture became much more elaborate.

The castles of the Middle Ages, which sometimes occupied a space of many acres, were usually built on high ground, or close to a river or the sea-shore, and were almost always surrounded by a ditch or moat, which, if possible, was filled with water. Inside the moat was a high and very thick wall, generally with towers at intervals, especially at the corners, with a parapet to shelter the men fighting on the top of it, and with spaces called embrasures through which they could shoot arrows at the enemy. The principal gate was strongly defended by covering towers, and above it were holes through which melted lead, or boiling water, or hot pitch or sand could be thrown on the besiegers. The doorway was reached by a drawbridge, raised and lowered by chains, and was closed by a heavy door, or a strong grating called a portcullis. Smaller gates were the postern and the sally-port.

The space inside the outer wall was known as the outer bailey, inside which was another wall, also with towers and a gate, within which were dwellings and store-houses. This was the inner bailey; and within it was the most important part of the fortress, the high tower called the keep—a building of several floors, with walls 15 or even 20 feet thick—the last place of retreat when the rest of the castle was taken. On the ground floor, which had no windows, were the well, sometimes of immense depth, the dungeon, and the store-rooms. On the next floor, which was lighted by narrow loop-holes, were the soldiers' quarters. On upper floors were the chapel and the apartments of the governor and his family.

There were nearly twenty Norman and mediaeval castles in Devonshire, few of them large or elaborate from the military point of view, and some, perhaps even the majority of them, insignificant in size and simple in style. Of some of these twenty strongholds no trace remains. Almost all, of which anything survives, are ruinous and uninhabitable. And although a few have been partially restored and are now occupied as dwelling-houses, only one, that of Powderham, retains its ancient dignity, after continuous occupation that has lasted for nearly six centuries. Comparatively little is known of the history of these castles; but many of them have been the scenes of fighting, especially in Norman times, in the reign of Henry VIII and during the Civil War.

One of the most famous and at the same time one of the oldest of Devonshire castles, is that of Exeter, called Rougemont from the colour of the rock on which it stands, built in 1067 by William the Conqueror on the site of an earlier fortress constructed by Athelstan, destroyed by Sweyn, and restored by Cnut and Edward the Confessor. Its first Norman governor was Baldwin de Brioniis, the Conqueror's nephew by marriage. It, or the city round it, has sustained many sieges; by the Saxons, by the sons of Harold, by King Stephen, by the Yorkists, by rebel armies, by Royalists and Parliamentarians, but it was ruinous even when Fairfax captured Exeter in 1646. A mere fragment, consisting chiefly of the gateway tower, is all that now remains of it.

The picturesque ruins of Okehampton Castle, built, it is believed, in the thirteenth century, partly of water-worn stones from the river below, and dismantled by order of Henry VIII, stand in a strong position above the West Okement, and include the remains of many rooms and of a great banqueting hall. A French prisoner of war has left a Latin inscription cut in one of the stones.

The remains of the ancient castle of Berry Pomeroy—founded, as some think, in the reign of William I—the most picturesque ruin in Devonshire, standing on a rocky eminence surrounded by dense woods three miles north-east of Totnes, consist principally of two towers, and of the gate-house and the chapel, whose fine masonry, much of which is thirteenth century work, is overgrown with moss and ivy. Inside the original building stands a very large but unfinished mansion, of great magnificence, begun by Lord Seymour, to whom, when Sir Thomas Pomeroy was deprived of his estates because of his share in the Commotion of 1549, the castle was given. The property still belongs to the Duke of Somerset, and has thus been in the hands of only two families since the Norman Conquest.

Compton Castle, about two miles west of Torquay, a very strongly fortified manor-house of the early fifteenth century built on the site of a castle of William I's time, is specially interesting from its association with Sir Humphrey Gilbert. It is now occupied as a farm. Nearness to the sea, and the consequent danger from the raids of foreign invaders, led to the strength of its defences. The building, which is large and picturesque, includes a number of ancient features, especially the chapel and two gateways.