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
Butter-churn tower Tower" and the bergfried of Idstein Castle) and Oberwesel (the "Oxen Tower"). The Marksburg above Braubach am Rhein had a square bergfried to which was added a small butter-churn turret in 1468. This burned down in 1705 and was replaced in 1905. One of the tallest towers is the 56-metre-high Round Tower, the symbol of the town of Andernach, which dates to 1453 and has an unusual variation: an octagonal upper turret with a stone gable roof. The highest bergfried of a hill castle with a butter-churn top (1370) was that of Rheinfels Castle above Sankt Goar am Rhein which