Romanesque Architecture...
...was common in Europe from about the mid-11th century to the advent of Gothic architecture. A fusion of Roman, Carolingian and Ottonian, Byzantine, and local Germanic traditions, it was a product of the great expansion of monasticism in the 10th–11th century.
Romanesque architecture characteristically incorporates semicircular arches for windows, doors, and arcades; barrel or groin vaults to support the roof; massive piers and walls, with few windows, to contain the outward thrust of the vaults; side aisles with galleries above them; a large tower over the crossing of nave and transept; and smaller towers at the one end.