Rome-born architect, urban designer, and archaeologist of French descent. He designed the Villa Pianciani, Terraja, between Spoleto and Todi (1784), and carried out major works of restoration and reconstruction at the Cathedral, Urbino (from 1789), where he drew on Palladian precedents, but his rigorous attention to architectural unity was influenced by Neo-Classicism. From 1800 he worked for Prince Stanisław Poniatowski (1757–1833), for whom he built the villa (and laid out the gardens) on the Via Flaminia, Rome (completed 1818), later remodelled (1824–44) by his pupil Canina. Around the same time he rebuilt the severe gate at the Ponte Milvio (1805), was consulted on the design of the Palazzo Braschi, Rome (1790–1804), and designed the façade of San Pantaleo, Rome (1806), robustly Neo-Classical in style, opposite the Palazzo Braschi. His most significant work, however, was the reorganization of the Piazza del Pòpolo (designed 1794–1811 and built 1816–24), where he created two huge hemicycles (with walls decorated with sphinxes and other Neo-Classical devices) around the Ancient Egyptian red-granite obelisk which Augustus had brought to Rome in 10 bc, and which Pope Sixtus V (1585–90) caused to be re-erected on its present site in 1589. Steps and ramps ascend to Valadier's triple-arched Loggiato (1816–20) and the terraced garden on the Pincio at the top of which he built the Casinò Valadier (1813–17), an original design with different elevations on all four sides. This work of eclectic Picturesque Classicism, as remarkable as anything by Jappelli, has Greek Doric loggie surmounted by Ionic columns, a curved entrance-portico with Ionic columns carrying a Doric frieze, and vaulted interiors decorated with Neo-Antique frescoes.
He also carried out extensive restoration works on various Ancient Roman buildings, including the arch of Titus, the Colosseum, the Temple of Fortuna Virilis, and Trajan's column. He designed the circular Church of Santa Cristina, Césena (1814–25), and reworked Palladian themes for church-fronts for his new façade for the Church of San Rocco, Rome (1833–4), drawing on San Giorgio Maggiore, Venice, for his precedent. He published Progetti (1807), Opere d'Architettura e di Ornamente (1833), and many other works, some of which deal with his multifarious activities as a restorer.
Debenedetti (1979);Debenedetti (ed.) (1985);P. Hoffmann (1967);Lapadula (1969);Marconi (1964);Meeks (1966);Placzek (ed.) (1982);Schulze-Battman (1939);Jane Turner (1966);