Dōn'jon, n.

noun

(dŭn'jun), n. [See DUNGEON.] A massive tower in ancient castles, regarded as the strongest part of the fortifications, and usually in the center of the whole, into which the garrison could retreat in case of necessity; — also denominated the keep. It was often used as a place for confining prisoners. [See Illust. of Castle.]

An old stone castle with several tall towers stands on a raised platform reached by steps.