<P> In the Quattrocento, concepts of architectural order were explored and rules were formulated . (See - Characteristics of Renaissance Architecture, below .) The study of classical antiquity led in particular to the adoption of Classical detail and ornamentation . </P> <P> Space, as an element of architecture, was utilised differently from the way it had been in the Middle Ages . Space was organised by proportional logic, its form and rhythm subject to geometry, rather than being created by intuition as in Medieval buildings . The prime example of this is the Basilica di San Lorenzo in Florence by Filippo Brunelleschi (1377--1446). </P> <P> During the High Renaissance, concepts derived from classical antiquity were developed and used with greater surety . The most representative architect is Bramante (1444--1514) who expanded the applicability of classical architecture to contemporary buildings . His San Pietro in Montorio (1503) was directly inspired by circular Roman temples . He was, however, hardly a slave to the classical forms and it was his style that was to dominate Italian architecture in the 16th century . </P> <P> During the Mannerist period, architects experimented with using architectural forms to emphasize solid and spatial relationships . The Renaissance ideal of harmony gave way to freer and more imaginative rhythms . The best known architect associated with the Mannerist style was Michelangelo (1475--1564), who frequently used the giant order in his architecture, a large pilaster that stretches from the bottom to the top of a façade . He used this in his design for the Campidoglio in Rome . </P>

The proportions of the sistine chapel paralleled the proportions of which ancient monument