A
keep (from the Middle English
kype) is a type of
fortified tower built within
castles during the
Middle Ages by European
nobility. Scholars have debated the scope of the word
keep, but usually consider it to refer to large towers in castles that were fortified residences, used as a refuge of last resort should the rest of the castle fall to an adversary. The first keeps were made of timber and formed a key part of the
motte-and-bailey castles that emerged in
Normandy and
Anjou during the 10th century; the design spread to
England as a result of the
Norman invasion of 1066, and in turn spread into
Wales during the second half of the 11th century and into
Ireland in the 1170s. The Anglo-Normans and French rulers began to build stone keeps during the 10th and 11th centuries; these included Norman keeps, with a square or rectangular design, and circular
shell keeps. Stone keeps carried considerable political as well as military importance and could take up to a decade to build.