The Catalan districts came into being just as the Romanesque style emerged. Romanesque architecture particularly distinguished itself in churches, monasteries and convents. During the 9th and 10th centuries, pre-Romanesque architecture, with its characteristic horseshoe arches, continued to dominate. The early Romanesque developed during the course of the 11th century. The walls, built of irregularly-shaped ashlar, were decorated with strips and blind arcades. The second, more sophisticated Romanesque style appeared in the 12th century. Sculptural motifs decorated windows and façades, while the walls were by now being constructed of even-shaped ashlar.