The plan consists of a nave of eight bays, two of which form a kind of vestibule, and five avenues, _i.e._ two aisles on each side; transepts of four bays each, with single aisles; and a choir of four bays and an apse, the double aisle of the nave being continued and carried down the choir. That part of the outer aisle which sweeps round the apse has been formed into a series of seven polygonal chapels, thus gaining a complete _chevet_.[24] Over the crossing there is a comparatively slender spire, and at the west end stand two massive towers terminated by a pair of lofty and elaborate spires, of open tracery, and enriched by crockets, finials, and much ornamentation. The cathedral is built of stone, without much variation in colour; it is vaulted throughout, and a forest of flying buttresses surrounds it on all sides. The beauty of the tracery, the magnificent boldness of the scale of the whole building, and its orderly regularity, are very imposing, and give it a high rank among the greatest works of European architecture; but it is almost too majestic to be lovely, and somewhat cold and uninteresting from its uniform colour, and perhaps from its great regularity. Strasburg Cathedral--not so large as Cologne--has been built at various times; the nave and west front are the work of the best Gothic period. This building has a nave and single aisles, short transepts, and a short apsidal choir. There is great richness in much of the work; double tracery, _i.e._ a second layer, so to speak, of tracery, is here employed in the windows, and extended beyond them, but the effect is not happy. The front was designed to receive two open tracery spires, but only one of them has been erected. It is amazingly intricate and rich, the workmanship is very astonishing, but the artistic effect is not half so good as that of many plain stone spires. Another important German church famous for an open spire is the cathedral at Friburg. Here only one tower, standing at the middle of the west front, was ever intended, and partly because the composition is complete as proposed, and partly because the design of the tracery in the spire itself is more telling, this building forms a more effective object than Strasburg, though by no means so lofty or so grandiose. [Illustration: FIG. 43.--CHURCH OF ST. BARBARA AT KUTTENBERG. EAST END. (1358-1548.)]