[Illustration: FIG. 12.--LINCOLN CATHEDRAL. (MOSTLY EARLY ENGLISH.)] In domestic and monastic buildings, low towers were frequently employed with excellent effect. Many castles retained the Norman keep, or square strong tower, which had served as the nucleus round which other buildings had afterwards clustered; but where during the Gothic period a castle was built, or rebuilt, without such a keep, one or more towers, often of great beauty, were always added. Examples abound; good ones will be found in the Edwardian castles in Wales (end of thirteenth century), as for example at Conway and Caernarvon. _Gables._ The gable forms a distinctive Gothic feature. The gables crowned those parts of a great church in which the skill of the architect was directed to producing a regular composition, often called a front, or a façade. The west fronts of Cathedrals were the most important architectural designs of this sort, and with them we may include the ends of the transepts and the east fronts. The same parts of parish churches are often excellent compositions. The gable of the nave always formed the central feature of the main front. This was flanked by the gables, or half-gables, of the aisles where there were no towers, or by the lower portions of the towers. As a rule the centre and sides of the façade are separated by buttresses, or some other mode of marking a vertical division, and the composition is also divided by bands of mouldings or otherwise, horizontally into storeys. Some of the horizontal divisions are often strongly marked, especially in the lower part of the building, where in early examples there is sometimes in addition to the plinth, or base of the wall, an arcade or a band of sculpture running across the entire front (_e.g._ east front of Lincoln Cathedral). The central gable is always occupied by a large window--or in early buildings a group of windows--sometimes two storeys in height. A great side window usually occurs at the end of each aisle. Below these great windows are introduced, at any rate in west fronts, the doorways, which, even in the finest English examples, are comparatively small. The gable also contains as a rule one or more windows often circular which light the space above the vaults. [Illustration: FIG. 13.--ST. PIERRE, CAEN, TOWER AND SPIRE. (SPIRE, 1302.)]