THE NEW ARCHITECTURE
In order to meet new needs, the Romanesque churches began to use the architectural feature of the round-headed arch for the openings, with semi-circular apses, covered by dome shape vaults, the buildings were increasingly covered with a stone barrel vault. This was the architectural style in which Roman, Bizantine and Carolingian styles blended together with the additions of new elements of Germanic origin.
The most commonly adopted plan, was based on an ancient basilica plan with a large central nave, an apse and two aisles. The use of the barrel vault (being particularly heavy) made the use of external buttresses necessary and a limited number of openings: two fundamental features of the Romanesque style, which is often termed «the art of the wall», was the use of half pilasters and archivolts in order to strengthen the barrel vault, thereby tending to split up the nave, contrasting it greatly to the style of Carolingian and Ottonian buildings.