Between the end of 1400 and beginning 1500 George of Challant, prior of Sant’Orso and great humanist-benefactor, orders to build, beside the church of S. Orso, the priory:a luxurious residence used for representation, a building inspired by the modern public buildings of Piedmont and Lombardy.It is a mix between new and old:the facade is in Renaissance style, with the window frames decorated by terracotta panels; other elements like the octagonal tower and ogives are a heritage of Gothic architecture.Inside the frescoes of the chapel are worth noticing, works created by end of the XV century Franco-Valdostan artists.