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
Addleshaw Tower 2008. The tower is the headquarters of the Chester Diocesan Guild of Church Bell Ringers. The Addleshaw Tower is the first free-standing bell tower to be built by an English cathedral since the 15th century. It has a square plan and is high. The tower is built on a reinforced concrete frame. The base is faced in local pink sandstone, and contains an entrance on the southwest side, with windows on the other three sides. One window on each side contains Dalle de verre stained glass, and these are flanked by smaller pairs of windows. The entrance is deeply recessed