The building is of Ancaster stone from Lincolnshire, and is said to have been paid for with coal from the Wollaton pits owned by Willoughby; the labourers were also paid this way. Cassandra Willoughby, Duchess of Chandos recorded in 1702 that the master masons, and some of the statuary, were brought from Italy. The decorative gondola mooring rings carved in stone on the exterior walls offer some evidence of this, as do other architectural features. There are also obvious French and Dutch influences. The exterior and hall have extensive and busy carved decoration, featuring strapwork and a profusion of decorative forms. The window tracery of the upper floors in the central block and the general busyness of the decoration look back to the Middle Ages, and have been described as "fantasy-Gothic".