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
Salisbury Cathedral spire, which at dominated the Wiltshire skyline from 1320. Because most of the cathedral was built in only 38 years, it has a single consistent architectural style, Early English Gothic. Although the spire is the cathedral's most impressive feature, it has proved to be troublesome. Together with the tower, it added 6,397 tons (6,500 tonnes) to the weight of the building. Without the addition of buttresses, bracing arches and anchor irons over the succeeding centuries, it would have suffered the fate of spires on other great ecclesiastical buildings (such as Malmesbury Abbey, 1180 to 1500; Lincoln Cathedral, 1311 to 1549;