 From his Milan base he reorganized the University of Pavia (1770) and the palazzo for the Accademia di Scienze e Belle Lettere, or Accademia Virgiliana, at Mantua (1773), 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

With the Habsburg decision permanently to install an archduke at Milan, Piermarini was commissioned to reconstruct the ducal palace adjoining the cathedral as an appropriate city residence and to construct a wholly new country seat near Monza.For the Royal Palace of Milan, Piermarini successfully avoided competition with the rich Gothic front of the cathedral with his sober neoclassical façade (1773–80) and created the Piazzetta Reale, as part of his urbanistic projects in the city centre.