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
Flanking tower and at the manor house of Hugenpoet Palace; Wellheim Castle has a square flanking tower. In church architecture, a flanking tower is a semi-circular or polygonal (for example, octagonal) tower on the outer wall of the church. The church of Great St. Martin Church in Cologne has several flanking towers. Flanking tower A flanking tower is a fortified tower that is sited on the outside of a defensive wall or other fortified structure and thus forms a flank. From the defensive platform and embrasures the section of wall between them (the curtain wall) could be swept from the side by