Free book for science fiction or history! GET EITHER OR BOTHFree Books!

Building a Castle: Concentric Castles

Walls around castles

When a child draws a picture of a castle, it tends to be a single building. But castles comprise several buildings, and usually two rings of walls. The value of concentric defences was known long before castles existed, in tribal hill forts. The word ‘concentric’ is a little misleading, as the walls were not circular, merely surrounding the site of the castle.

Belvoir Castle, Jerusalem

The first dateable concentric castle was Belvoir Castle in the crusader kingdom of Jerusalem. It was built by Gilbert of Assailly, Grand Master of the Knights Hospitaller, started in 1168. It was built on a high plateau about 20km south of the Sea of Galilea. It overlooks the River Jordan 500m below and was so high and inaccessible that the Muslims called it an eagle’s nest or home of the moon.

The concentric design had many advantages. While we have already discussed the curtain wall, but the higher inner wall allowed defenders to give devastating fire both to the outer wall and if the attackers gained access to the outer ward. It also provided a means of retreat should the outer defences be breached.

The design worked. Belvoir withstood a siege by Saladin’s army for 18 months. A similar castle, Krak des Chevaliers in Syria, was so well fortified that Saladin turned away from a siege.

Beaumaris Castle plan

The most perfect concentric castle is considered to be Beaumaris Castle on Anglesey, North Wales. The inner curtain wall was 11m high and 4.7m thick, with six defensive towers and two gatehouses with twin D-shaped towers. The octagonal outer wall has twelve towers and two gatehouses and overlooks a moat.

Built for Edward I between 1295 and 1300, and then 1306 to 1330, the total cost was £15,000.

[adapted from The Medieval Castle Haynes Manual by Charles Phillips]

Ann Marie Thomas is the author of four medieval history books, a surprisingly cheerful poetry collection about her 2010 stroke, and the science fiction series Flight of the Kestrel. Book one, Intruders, and book two Alien Secrets, are out now. Follow her at