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
Toledo Cathedral the town hall and the Archbishop's Palace. To the left is the bell tower and to the right the projecting Mozarabic chapel that occupies the place where the second tower was to be built. To the left of the main façade rises the only tower of the cathedral. The dome that is seen to the right belongs to the Mozarabic chapel which was commissioned by Cardinal Cisneros. The tower has two parts: the lower part, of square cross-section, was designed by Alvar Martínez; the upper, octagonal part was designed by Hanequin de Buselas. It is topped by a spire. The