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
Rochester Cathedral the northern end of the west wall. To the east of the north transept is the Sextry Gate. It dates from Edward III's reign and has wooden domestic premises above. The area beyond was originally enclosed, but is now open to the High Street through the memorial garden and gates. Beyond the Sextry Gate is the entrance to Gundulf's Tower, used as a private back door to the cathedral. The north quire transept and east end are all executed in Early English style, the lower windows light the crypt which is earlier. Adjoining the east end of the cathedral is