The dome is very cleverly planted on eight piers instead of four at the crossing, and is a triple structure; for between the dome seen from within, and the much higher dome seen from without, a strong cone of brickwork rises which bears the weight of the stone lantern and ball and cross that surmount the whole. The skill with which the dome is made the central feature of a pyramidal composition whatever be the point of view, the great beauty of the circular colonnade immediately below the dome, the elegant outline of the western towers, and the unusual but successful distribution of the great portico, are among the most noteworthy elements which go to make up the charm of this very successful exterior. [Illustration: FIG. 82.--ST. PAUL'S CATHEDRAL, LONDON. (1675-1710.)] Wren may be said to have introduced to Renaissance architecture the tower and spire, for though many examples occur in Spain, there is reason to suppose that he was before the architects of that country in his employment of that feature. He has enriched the City of London with a large number of steeples, which are Gothic so far as their general idea goes, but thoroughly classic in details, and all more or less distinctive. The most famous of these is the one belonging to Bow Church; others of note belong to St. Clement Danes and St. Bride, Fleet Street. The interiors of some of these churches, as for example St. Stephen, Walbrook, St. Andrew, Holborn, and St. James, Piccadilly, are excellent both for their good design and artistic treatment, and for their being well contrived and arranged for the special purposes they were intended to fill.