To an unpractised eye the light relievos and fanciful arabesques which cover the walls of the Alhambra appear to have been sculptured by the hand, with a minute and patient labor, an inexhaustible variety of detail, yet a general uniformity and harmony of design truly astonishing; and this may especially be said of the vaults and cupolas, which are wrought like honey-combs, or frostwork, with stalactites and pendants which confound the beholder with the seeming intricacy of their patterns. The astonishment ceases, however, when it is discovered that this is all stucco-work: plates of plaster of Paris, cast in moulds and skilfully joined so as to form patterns of every size and form. This mode of diapering walls with arabesques and stuccoing the vaults with grotto-work, was invented in Damascus, but highly improved by the Moors in Morocco, to whom Saracenic architecture owes its most graceful and fanciful details. The process by which all this fairy tracery was produced was ingeniously simple: The wall in its naked state was divided off by lines crossing at right angles, such as artists use in copying a picture; over these were drawn a succession of intersecting segments of circles. By the aid of these the artists could work with celerity and certainty, and from the mere intersection of the plain and curved lines arose the interminable variety of patterns and the general uniformity of their character.
Washington Irving Tales From the Alhambra
from Cheri Lucas of Writing Through the Fog