If the imperial effort in France barely extended outside Paris except for the interior alterations that Percier and Fontaine carried out in the royal châteaux at Versailles, Compiègne, Saint-Cloud, and Fontainebleau—major examples of Empire decoration but not of architecture—the emperor and his nominees left their mark on most of the great cities of continental Europe. The Palazzo Serbelloni in the Corso Venezia, where Napoleon stayed in Milan, had been built by Simone Cantoni (1736-1818) in 1794. Similar to French work of the 1780s, it would probably have impressed the Emperor as still quite up-to-date. He ordered in 1806 the laying out in Milan of the Forum Bonaparte, according to the designs of Giannantonio Antolini (1754-1842), and the erection of a conventionally Roman triumphal arch, the work of Luigi Cagnola (1762-1832?), which was finally completed in 1838. In Rome the development of the Piazza del Popolo, like the Forum Bonaparte a work of urbanism rather than of architecture, was based by Giuseppe Valadier (1762-1859), an Italian despite his French name and ancestry, on a project he had made as early as 1794. This project was modified by him under the Empire to incorporate ‘corrections’ by the younger Gisors and L.-M. Berthault (1771?-1823). Execution of the project actually began only in 1813 after Pope Pius VII returned from his Napoleonic captivity; Valadier carried it forward to ultimate completion in 1831. Valadier’s Roman church work, such as his new façade for San Pantaleone of 1806, just off the present-day Corso Vittorio Emanuele, is mostly too dull to mention; his domestic work was somewhat more interesting, but with little personal or even Italian flavour. In Naples Leconte, who had worked with the two Gisors on the Salle des Cinq Cents in Paris, remodelled the San Carlo opera house in 1809 for Murat—it was, however, refronted in 1810-12 and rebuilt in 1816-17 (see Chapter 3). In association with Antonio de Simone, Leconte also decorated rooms in the Bourbon Palace at Caserta,[32] originally built by Vanvitelli in 1752-74, for this Napoleonic brother-in-law. But the finest Empire things in the area were the Sala di Marte and the Sala di Astrea there, which de Simone, working alone, had begun to decorate slightly earlier in 1807 for Napoleon’s brother Joseph Bonaparte (Plate 25). As with so many architectural projects of the brief period of the Empire, it was left to a returning legitimate sovereign, in this case Ferdinand I of the Two Sicilies, to finish the job. Unlike the greater part of Percier and Fontaine’s work in the French palaces, these rooms at Caserta are interior architecture, not just interior decoration, and fully worthy in their scale and their sumptuous materials of the magnificent spaces, created almost half a century earlier by Vanvitelli, which they occupy. This is the more remarkable as de Simone was really a decorator not an architect.