Though located in the Old Montreal historic district, it is an international style structure, featuring the outdoor sculpture Allegrocube.

The black metal and granite building is adjacent to the Champ de Mars square.

It was designed by Montreal architects Pierre Boulva and Jacques David, whose other prominent Montreal projects included 500 Place D'Armes, Théâtre Maisonneuve, the Dow Planetarium and the Place-des-Arts, Atwater and Lucien-L'Allier metro stations.

[3][4] Created by Charles Daudelin in 1973, Allegrocube is a cube-shaped abstract sculpture outside the Palais, 2.4 m in height, made of bronze.

The first was the Old Montreal Courthouse, now known as the municipal Édifice Lucien-Saulnier, designed by John Ostell (as well as Frederick Preston Rubidge) and inaugurated in 1856.