Career
He was Vanvitelli's collaborator at Caserta, then he removed to Milan. From his Milan base he reorganized the University of Pavia and the palazzo for the Accademia di Scienze e Belle Lettere, or Accademia Virgiliana, at Mantua, where he also designed the façade of the neighbouring Teatro Bibiena. He designed the interior of the Maria Teresa Hall of the Biblioteca Braidense in Milan.
For the Royal Palace of Milan, Piermarini successfully avoided competition with the rich Gothic front of the cathedral with his sober neoclassical façade and created the Piazzetta Reale, as part of his urbanistic projects in the city centre. For the Royal Villa of Monza, successive changes adapted the original pleasure villa to a seat of court.
In 1779 Piermarini was officially named architect of the Imperial Kingdom, a position he had occupied in fact for several years.
ver the years successive internal reconstructions have altered the interior of the Teatro alla Scala, so that only Piermarini's general plan, and his facade, are what remain of his designs.
In 1798 he returned to his native Foligno, where he effected some changes in the Duomo and prepared a project for the Cappella del Sacramento in the church of San Lorenzo at Spello. Among his pupils was Giacomo Albertolli, the nephew of Piermarini's collaborator in stucco decoration of palaces, Giocondo Albertolli. Giacomo succeeded him as professor of architecture in the Brera Academy.