The specific character of the Romanesque style can be understood only in the light of the development of early medieval architecture in the West, notably its Carolingian and Ottonian phases. Certain of the most characteristic features of Romanesque structures—the massive west facade crowned by a tower or by twin towers, the complex design of the eastern part housing the sanctuary, the rhythmic alternation of piers and columns in the nave—represent only the advanced stages in a lengthy and complex formal evolution marked by considerable trial and error.
The development of Romanesque architecture owes much to the primacy accorded to vaulting. Masonry vaulting (see vault) since the beginning of Christian architecture had been confined to buildings of relatively small scale and to crypts. Large basilican structures, in a continuation of a tradition inaugurated by the early Christian basilica, were topped by wooden roofs. Romanesque churches, on the other hand, with notable exceptions in Normandy and Italy, sustained massive barrel vaults, making mandatory the reinforcement of load-bearing walls in order to parry the lateral outward thrust. The frequent presence of galleries above the aisles, sometimes with half-barrel vaults, is in all probability rooted in structural considerations connected with the problem of abutment. The limitation of wall openings to a minimum, related to the same concern, contributed to the sober yet somberly impressive character of the light.
The major share of architectural activity was sponsored by the great monastic communities. The Cluniac order, at the peak of its power, played a primary role in the patronage of construction. Thus a number of significant Cluniac churches connected with great 12th-century pilgrimages—St. Martin in Tours, St. Sernin in Toulouse, and Santiago de Compostela in Spain—show great similarity in plan and overall design. This sameness is especially notable in the presence of spacious ambulatories with radiating chapels designed to facilitate the pilgrims' access to the precious relics. The design of the third church of Cluny, dedicated in 1095, is reflected in a number of Burgundian churches. The basilica of San Marco in Venice and other Byzantine structures help to account for the presence of domed vaulting in a group of churches in French Aquitaine. German Romanesque architecture on the other hand remained strongly tied to the heritage of Ottonian art.
The following structures are noted works of Romanesque architecture: France—the abbey churches of St. Madeleine Vézelay (c.1090–1130) and Paray-le-Monial (early 12th cent.); Germany—the Cathedral of Speyer, dedicated in 1060, but largely reconstructed after 1082, and the Church of St. Mary on the Capitol in Cologne (1049); Italy—the cathedral (1063–92) and baptistery (1153) in Pisa, the Church of San Miniato al Monte (c.1070) in Florence, and the Cathedral of Monreale in Sicily (1174). From the last third of the 12th cent. certain features of the churches in N France and in England began to point toward the development of the Gothic (see Norman architecture). Similarly, architecture in the Ile-de-France, particularly the ambulatory (1140) of the abbey of St. Denis, reveals such an advance in unified design and construction as to be considered the first monument of Gothic architecture.