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
Ivan the Great Bell Tower of Cathedral Square. The tower itself consists of three octagonal drums, narrowing towards the top, and surmounted by a golden dome and seven-meter high cross. Each section has cut-out windows for the bells, and the upper third has a series of "kokoshnik" ornamentation (which marks the translation between the 1509 original and the 1600 addition). Inside the tower a total of 329 steps long spiral staircase leads to the highest observation deck. The space on the ground floor of the base was once home to the Church of St. John Climacus and is cramped due to the walls being five