The quire and nave and octagonal corona are fairly uniform in style but surprisingly otherwise in plan. They belong to that period of Gothic architecture when lancets were just giving place to traceried windows, and clustered shafts and foliage caps and deeply-moulded arches were more beautiful than after or before. The works were in progress through much of the thirteenth and fourteenth centuries, and evidently dragged on long. A bad fire gave a serious set-back in 1328. It is doubtful whether the nave was ever done. It was begun as early as 1248 by Archbishop Sigurd, son of one of the brave birkebeiner or birchlegs, who had helped King Sverre to his throne. The builders of each part seem to have been profoundly unconscious of what their colleagues elsewhere had been about. For they were working on the foundations of three little older churches. St. Clement's was built originally by St. Olaf himself, his son Magnus the Good raised a church over his later grave where now the corona stands, a stone church of St. Mary was erected by Harald Hardredy (p. 95) on the site of the quire.[36] Most awkwardly St. Clement's joins the rest of the church; the beautiful aisle-encircled corona declines to meet the quire at any understandable angle, the walls and pillars of the quire itself trend apart on either side toward the east.[37] See plan opposite p. 246. [Illustration: NORTH-EAST CORNER OF QUIRE, LOOKING INTO AISLE AND CORONA] [_Face page 86_ Over the great central tower, which long was cut off by a low metal roof, have been raised a tall spire of wood and four pinnacles of stone. It is largely this lofty steeple in the centre that gives the Cathedral so English a look. The magnificence of this fair church is all the more striking when one realises that, with a few most unimportant exceptions, it is the furthest north of all the buildings of the middle ages. Yet its equal is not to be found in any part of Europe further south, till the latitude of Glasgow is reached.