Carlo Marchionni

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, who designed the (Petit Trianon) Marchionni's earliest training was as a sculptor.

He studied architecture at Rome's Accademia di San Luca, as pupil of Filippo Barigioni, who favored the elaborated style of Borromini.

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.

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.

Giovanni Domenico Porta's commemorative canvas from 1776 (now in Palazzo Braschi) shows Pope Pius presenting two large sheets depicting a plan and elevation, which are open upon a draped table.

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 honor Pope Benedict XIII.

While Winckelmann had declared the Villa Albani "the most beautiful building of our time", in a famous letter from Francesco Milizia to the Venetian connoisseur Zulian Milizia dismissed "Marchionnisti", "Michelangiolisti", "Berniniani" and "Borrominiani" as reactionary obscurantists who execrated the young Antonio Canova's fully classical monument to Pope Clement XIV of 1787.