Italian architect, sculptor, and draftsman. Marchionni's early career was fostered by his lifelong friend Cardinal Alessandro Albani, a great collector of antiquities. His mature style exhibits a richly-detailed idiomatic repertory on the cusp of Late Baroque and Neoclassicism that may be compared with the similar style by his Italian contemporaries Alessandro Galilei, Ferdinando Fuga or Vanvitelli, or indeed with their French contemporary, Ange-Jacques Gabriel. Marchionni's earliest training was as a sculptor. He studied architecture at Rome's Accademia di San Luca, as pupil of Filippo Barigioni (1690-1753), who favoured the elaborated style of Borromini. In 1728 Marchionni had come to Albani's attention after winning first prize in the Academy's Concorso Clementino. Marchionni's Borromini-influenced style is identifiable in Marchionni's early work (1728) for Cardinal Albani's villa at Anzio and at the papal retreat of Castel Gandolfo. Marchionni helped restore and rebuild the choir at San Giovanni in Laterano along with Giovanni Battista Piranesi, whose picturesque approach to Roman antiquity likely influenced Marchionni's style. However, Marchionni's mature work, such as the Villa Albani (1746-63) expresses the courtly decorative classicism of his patron's circle, which included the neoclassicist Winckelmann, curator of Albani's antiquities. After Niccolò Salvi's death in 1751, Marchionni help design the Villa's garden façade. Marchionni was appointed papal architect and overseer of works at St Peter's Basilica by Pope Benedict XIV. In 1766, the pope commissioned Marchionni to rebuild the entrance façade of the Museo Profano, the papal collection of antiquities originally displayed by Bramante in the Braccia Nuova of the Vatican, along one side of the Cortile del Belvedere. Two commissions from Pope Pius VI constituted Marchionni's last official Roman projects. One was the new sacristy for St Peter's (1776-84), which had been envisaged by the preceding pontiff, who demolished the mausoleum dedicated to the Madonna of the Fevers that stood on its site. The project was preceded by a public competition. The imposing Sacristy, an independent building as large as a church, is sited in the angle of the left transept. It consists of the octagonal Sagrestia Comune, the Sacristy of the Canons, and the Sala of the Chapter. It is connected to the basilica by raised galleries in which Marchionni inserted fragments of Roman bas reliefs. Marchionni also designed church furnishings, such as the high altar and rich tabernacle of Santa Caterina a Magnanapoli (1787). Cardinal Albani commissioned from Marchionni the funerary monument (1737-39) located in Santa Maria sopra Minerva, with sculpture by his frequent collaborator Pietro Bracci, to honour Pope Benedict XIII. Outside Rome, Cardinal Albani commissioned a façade for the collegiate church at Nettuno (1734). He received papal commissions for the churches of San Domenico in Ancona (from 1763) and Santa Maddalena de Cassinessi in Messina (from 1765). As an engineer, he was responsible for work in the port of Ancona overseen by Luigi Vanvitelli. Throughout his career his scenographic talents were called upon for the temporary decorations required for public events, which are documented in preparatory drawings or presentation drawings. The developing Neoclassicism soon dismissed Marchionni's conservative classicised Baroque style. //