<P> The decoration of the exterior of the cathedral, begun in the 14th century, was not completed until 1887, when the polychrome marble façade was completed with the design of Emilio De Fabris . The floor of the church was relaid in marble tiles in the 16th century . </P> <P> The exterior walls are faced in alternate vertical and horizontal bands of polychrome marble from Carrara (white), Prato (green), Siena (red), Lavenza and a few other places . These marble bands had to repeat the already existing bands on the walls of the earlier adjacent baptistery the Battistero di San Giovanni and Giotto's Bell Tower . There are two side doors: the Doors of the Canonici (south side) and the Door of the Mandorla (north side) with sculptures by Nanni di Banco, Donatello, and Jacopo della Quercia . The six side windows, notable for their delicate tracery and ornaments, are separated by pilasters . Only the four windows closest to the transept admit light; the other two are merely ornamental . The clerestory windows are round, a common feature in Italian Gothic . </P> <P> During its long history, this cathedral has been the seat of the Council of Florence (1439), heard the preachings of Girolamo Savonarola and witnessed the murder of Giuliano di Piero de' Medici on Sunday, 26 April 1478 (with Lorenzo Il Magnifico barely escaping death), in the Pazzi conspiracy . </P> <P> The cathedral of Florence is built as a basilica, having a wide central nave of four square bays, with an aisle on either side . The chancel and transepts are of identical polygonal plan, separated by two smaller polygonal chapels . The whole plan forms a Latin cross . The nave and aisles are separated by wide pointed Gothic arches resting on composite piers . </P>

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