Romanesque architecture features round arches, wall arcades or buttresses, cylindrical apses and chapels, and square, round or polygonal towers. It was the dominant style in Europe from the 10th to 12th centuries, incorporating both classical and Byzantine elements. Romanesque churches were built on a grand scale with long naves, aisles, ambulatories, and radiating chapels to accommodate large numbers of pilgrims. Thick walls and small windows supported heavy stone vaults, while buttresses braced the walls against the outward thrust of the vaults.