Women's hair was already arranged high above the head, but Georgiana took the fashion a step further by creating the three-foot hair tower. She stuck pads of horse hair to her own hair using scented pomade and decorated the top with miniature ornaments. Sometimes she carried a ship in full sail, or an exotic arrangement of stuffed birds and waxed fruit, or even a pastoral tableau with little wooden trees and sheep. Even though the towers required the help of at least two hairdressers and took several hours to arrange, Georgiana's designs inspired others to imitate her. "The Duchess of Devonshire is the most envied woman of the day in the Ton," the newspapers reported. It was true; women competed with each other to construct the tallest head, ignoring the fact that it made quick movements impossible and the only way to ride in a carriage was to sit on the floor. (Georgiana: Duchess of Devonshire by Amanda Foreman, p. 36)
I had thought that hair-as-diorama had originated in ancien regime France, but I can't find a reference right now. So maybe it went from Britain to France -- Georgiana was friends with several important and influential French women, including the Duchesse de Polignac and Marie Antoinette.