+RHENISH CHURCHES.+ It was in the Rhine provinces that vaulting was first applied to the naves of German churches, nearly a half century after its general adoption in France. Cologne possesses an interesting trio of churches in which the Byzantine dome on squinches or on pendentives, with three apses or niches opening into the central area, was associated with a long three aisled nave (+St. Mary-in-the-Capitol+, begun in 9th century; +Great St. Martin’s+, 1150-70; +Apostles’ Church+, 1160-99: the naves vaulted later). The double chapel at +Schwarz-Rheindorf+, near Bonn (1151), also has the crossing covered by a dome on pendentives. [Illustration: FIG. 100.--ONE BAY OF CATHEDRAL AT SPIRES.] The vaulting of the nave itself was developed in another series of edifices of imposing size, the cathedrals of +Mayence+ (1036), +Spires+ (Speyer), and +Worms+, and the +Abbey of Laach+, all built in the 11th century and vaulted early in the 12th. In the first three the main vaulting is in square bays, each covering two bays of the nave, the piers of which are alternately lighter and heavier (Figs. 99, 100). At Laach the vaulting-bays are oblong, both in nave and aisles. There was no triforium gallery, and stability was secured only by excessive thickness in the piers and clearstory walls, and by bringing down the main vault as near to the side-aisle roofs as possible. +RHENISH EXTERIORS.+ These great churches, together with those of +Bonn+ and +Limburg-on-the-Lahn+ and the cathedral of +Treves+ (Trier, 1047), are interesting, not only by their size and dignity of plan and the somewhat rude massiveness of their construction, but even more so by the picturesqueness of their external design (Fig. 101). Especially successful is the massing of the large and small turrets with the lofty nave-roof and with the apses at one or both ends. The systematic use of arcading to decorate the exterior walls, and the introduction of open arcaded dwarf galleries under the cornices of the apses, gables, and dome-turrets, gave to these Rhenish churches an external beauty hardly equalled in other contemporary edifices. This method of exterior design, and the system of vaulting in square bays over double bays of the nave, were probably derived from the Lombard churches of Northern Italy, with which the Hohenstauffen emperors had many political relations. [Illustration: FIG. 101.--EAST END OF CHURCH OF THE APOSTLES, COLOGNE.] The Italian influence is also encountered in a number of circular churches of early date, as at Fulda (9th-11th century), Drügelte, Bonn (baptistery, demolished), and in façades like that at Rosheim, which is a copy in little of San Zeno at Verona. Elsewhere in Germany architecture was in a backward state, especially in the southern provinces. Outside of Saxony, Franconia, and the Rhine provinces, very few works of importance were erected until the thirteenth century.