St Paul's Cathedral familiar with the unique octagonal lantern tower over the crossing of Ely Cathedral, which spans the aisles as well as the central nave, unlike the central towers and domes of most churches. Wren adapted this characteristic in designing the dome of St Paul's. In section St Paul's also maintains a medieval form, having the aisles much lower than the nave, and a defined clerestory. The most notable exterior feature is the dome, which rises to the cross at its summit, and dominates views of the City. The height of 365 feet is explained by Wren's interest in astronomy. Until the
Ely Cathedral and transepts. Rows of trefoil heads and use of pointed instead of semicircular arches, results in a west front with a high level of orderly uniformity. Originally the west front had transepts running symmetrically either side of the west tower. Stonework details on the tower show that an octagonal tower was part of the original design, although the current western octagonal tower was installed in 1400. Numerous attempts were made, during all phases of its construction to correct problems from subsidence in areas of soft ground at the western end of the cathedral. In 1405-7, to cope with the extra