NOTWITHSTANDING very wide differences which undoubtedly exist, there is a sufficient bond of union between the Basilican, the Byzantine, and the Romanesque styles, to render it possible for us to include the characteristics of the three in an analysis of Christian round-arched architecture.
The Plan or floor-disposition of the basilican churches, as has been pointed out, was distinctive. The atrium, or forecourt, the porch, the division into nave and aisles; the transept, the great arch, and the apse beyond it with the episcopal seat at the back behind the altar; the ambos; and the enclosure for the choir, were typical features. Detached towers sometimes occurred. The plan  of Romanesque churches was based upon that of the basilica; the atrium was often omitted, so was the transept sometimes; but, when retained, the transept was generally made more prominent than in the basilica. The position of the altar and of the enclosure for the choir were changed, but in other respects the basilica plan was continued. In Germany, however, apsidal transepts (Fig. 178) were built. Towers were common, occasionally detached, but more frequently joined to the main building.
Circular and polygonal buildings for use as baptisteries,  and sometimes as churches, existed both in the basilican and the Romanesque time.
Byzantine church plans are all distinguished by their great central square space, covered by the central dome, flanked usually by four arms, comparatively short, and all of equal length; and the plan of the buildings is generally square, or nearly so, in outline. Circular and polygonal buildings sometimes occur.
Few traces of the arrangement of military, secular, or domestic buildings earlier than the twelfth century remain, but some examples of a cloister at the side of the nave (generally the south side) of a church, giving or intended to give access to monastic buildings, still exist.
The Walls of such buildings as have come down to us are, it may be well understood, strong, since the most recent of this round-arched series of buildings must be about seven hundred years old. Fine masonry was not much employed till the time of the Normans, but the Roman plan of building with bricks or rubble and casing the face of the walls with marble or mosaic, or at least plaster, was generally followed. The walls are carried up as gables and towers to a considerable extent (Fig. 179), especially in Western countries.
 The Roof.—In a basilica this was of timber, in a Byzantine church it consisted of a series of domes; in a Romanesque church it was sometimes of timber as in the basilica, but not unfrequently vaulted. As a general rule the vault prevailed in the West and the dome in the East; and such examples of either sort of roof as occur in those provinces where the other was usual, like the domed churches in parts of France, must be looked upon as exceptional.
The Openings are almost invariably arched, and seldom, if ever, covered by a lintel. It is hardly necessary to add that the arches are always round. Almost always they are semicircular, but instances of the employment of a segmental arch, or of one the outline of which is a little more than half a circle, may be occasionally met with.
Door openings are often made important both by size and decoration. Window openings are usually small; and the grouping of two or more lights under one head, which was so conspicuous a feature in Gothic architecture, first appears in Byzantine buildings, and is met with also in Romanesque ones. The mode of introducing light is to a certain extent characteristic. The basilican churches always possess a clerestory, and usually side windows in the aisles; and this arrangement is generally followed in Romanesque buildings, though sometimes, in Germany, the clerestory is omitted. The gable ends of the nave and transepts are not usually pierced by many or large lights (Fig. 180); and when there is a central feature, as a tower, or even a dome, little or no light is introduced through it. On the other hand, the Byzantine churches depend largely for light upon the ring of windows which commonly encircles the base of the central dome, and sometimes that of the subsidiary domes; and the gables are  pierced so as to supply any additional light required, so that windows are infrequent in the lower walls. Broadly speaking, therefore, the Western churches have side-lighting and the Eastern top-lighting.
The great arches which carry the main domes form a notable feature in Eastern churches, and are of very bold construction. In the basilican churches one great arch, called “the arch of triumph,” occurs, and only one; this gives access to the apse: and a similar arch, which we now denominate “the chancel arch,” usually occupies a corresponding position in all Romanesque churches. The arches of the arcade separating the nave from the aisles in all Western churches are usually of moderate span. In some ancient basilicas these arches are replaced by a horizontal beam.
The Columns.—In basilicas these were of antique type; very often they had actually been obtained by the demolition of older buildings, and when made purposely they were as a rule of the same general character. The same might be said of those introduced into Byzantine buildings, though a divergence from the classic type soon manifested itself, and small columns began to appear as decorative features. In Romanesque buildings the columns are very varied indeed, and shafts are frequently introduced into the decoration of other features. They occur in the jambs of doorways with mouldings or sub-arches springing from them; long shafts and short ones, frequently supporting ornamental arcades, are employed both internally and externally; and altogether that use of the column as a means of decoration, of which Gothic architecture presents so many examples, first began in the Romanesque style.
The capitals employed in Romanesque buildings  generally depart considerably from the classic type, being based on the primitive cube capital (Fig. 181), but, as a rule, in Eastern as well as in basilican churches, they bear a tolerably close resemblance to classic ones.
The Ornaments throughout the whole of the Christian round-arched period are a very interesting subject of study, and will repay close attention. In the basilican style mouldings occur but seldom: where met with, they are all of the profiles common in Roman architecture, but often rudely and clumsily worked. Carving partakes also of classic character, though it is not difficult to detect the commencement of that metamorphosis which was effected in Byzantium, and which can hardly be better described than in the following paragraph from the pen of Sir Digby Wyatt:—“The foliage is founded on ancient Greek rather than on Roman traditions, and is characterised by a peculiarly sharp outline. All ornamental sculpture is in comparatively low relief, and the absence of human and other figures is very marked. Enrichments were almost invariably so carved, by sinking portions only of the surfaces and leaving the arrises and principal places untouched, as to preserve the original constructive forms given by the mason (Fig. 184). The employment of the drill instead of the chisel, so common in debased Roman work, was retained as a very general practice by the Greek carvers, and very often with excellent effect. The foliage of the acanthus, although imitated from the antique, quite  changed its character, becoming more geometrical and conventional in its form. That which particularly distinguishes Lombard from Byzantine art is its sculpture abounding with grotesque imagery, with illustrations of every-day life, of a fanciful mythology not yet quite extinct, and allusions, no longer symbolic but direct, to the Christian creed; the latter quality a striking evidence of the triumph of the Roman Church over all iconoclastic adversaries in Greece.” What is here asserted of Lombard carving is true of that in the Romanesque buildings in Germany, Scandinavia (Fig. 182), France, and to a certain extent in Great Britain, though in our own country a large proportion of the ornamental carving consists simply of decorative patterns, such as the chevron, billet, and zig-zag; and sculpture containing figures and animals is less common.
The mouldings of Romanesque buildings are simple, and at first were few in number, but by degrees they become more conspicuous, and before the transition to Gothic they  assumed considerable importance (Fig. 183) and added not a little to the architectural character of the buildings.
Coloured decoration, especially in mosaic, was a conspicuous feature in basilican churches, and still more so in those of the Byzantine style; such decoration in  Romanesque churches was not infrequent, but it was more commonly painted in fresco or tempera. The glass mosaic-work to be found on the walls of Early Christian churches, both basilican and Byzantine, but less frequently Romanesque, is most interesting and beautiful: “it was,” says the high authority already quoted, “employed only to represent and reproduce the forms of existing objects, such as figures, architectural forms and conventional foliage, which were generally relieved with some slight indication of shading upon a gold ground—the whole being bedded in the cement covering the walls and vaults of the basilicas and churches.”
“The design of both figures and ornaments was, generally speaking, very rude, though not without an occasional rising in some of the figures to a certain sublimity, derivable principally from the great simplicity of the forms and draperies and the earnest grandiose expression depicted on their countenances. The pieces of glass employed in the formation of this work are very irregular in shapes and sizes, of all colours and tones of colour, and the ground tint almost invariably prevailing is gold. The manner of execution is always large and coarse, and rarely approaches in neatness of joint and regularity of bedding to the (ancient Roman) ‘opus majus vermiculatus;’ yet, notwithstanding these blemishes, the effect of gorgeous, luxurious, and at the same time solemn decoration produced is unattainable by any other means as yet employed as structural embellishment. How noble and truly ecclesiastical in character are the gold-clad interiors of Monreale Cathedral, of the Capella Palatina at Palermo, of St. Mark at Venice, San Miniato at Florence, or Santi Apollinare and Vitale at Ravenna, the concurrent testimony of all travellers attests.”
 A finer kind of glass mosaic arranged in geometrical patterns was made use of to enrich the ambos, screens, episcopal chairs, sepulchral ornaments, and other similar fittings of churches, and was often of great beauty. A third sort of mosaic—the Alexandrine work (opus Alexandrinum)—used for pavements, has been already alluded to; this was extremely effective, but its use appears to have been less general than that of the glass mosaics for the walls.
The Architectural Character of the basilican churches may be briefly characterised as venerable and dignified, but yet cheerful and bright rather than forbidding; they are, as interiors, impressive but not oppressive, solemn but not gloomy. Comparatively little attention was paid to external effect, and there is not often much in them to strike the passer-by. The character of Byzantine interiors is far more rich, and even splendid; but it is more gloomy, and often is solemn and grand to the last degree. In many cases these churches possess fine exteriors; and for the level sky-line produced by the long straight roofs of the basilica, a more or less pyramidal composition, showing curved outlines rather than straight ones, is substituted. The architectural character of the Romanesque buildings varies extremely with the districts in which they are erected; but, generally speaking, it may be described as picturesque, and even sometimes romantic; the appearance of towers, prominent transepts, and many smaller decorative features serves to render the exteriors telling and varied, though often somewhat rude and primitive. A solid and somewhat heavy character distinguishes the interiors of some varieties of Romanesque buildings—such, for example, as our own Early Norman; but in our fully-developed and late Norman, and still more in the latest  German Romanesque churches, this disappears almost entirely, and much beauty and even lightness of effect is obtained, without any loss of that richness which is characteristic of more ancient examples.