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
Down Cathedral medieval effect. Work was completed and the cathedral was ready for use in 1818. An octagonal vestibule and a Perpendicular Gothic tower were added to the west end in 1826. Crosses from the 9th, 10th and 12th centuries are preserved in the Cathedral. The building today is mainly the original chancel from the 15th century with a vestibule and tower added. It had a second major restoration from 1985 to 1987 during which time the Cathedral was closed. It houses an 11th-century granite font discovered in use as a watering trough in 1927 and installed in the Cathedral in 1931.