clerestory or clearstory (both: klĭrˈstōrˌē, –stôrˌē) [key], a part of a building whose walls rise higher than the roofs of adjoining parts of the structure. Pierced by windows, it is chiefly a device for obtaining extra light. It had an early use in certain Egyptian temples, as at Karnak, and was used later in the great halls of Roman basilicas. It became a characteristic element of medieval churches, receiving its fullest development in churches of the Gothic period.
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