In piazza Duomo, on the corner column of the Loggia, the Macia is still carved: it is a unit of length, the one by which goods were anciently checked in trade. Buyer and seller could go there and verify, because the measure was of stone and stood in public. Spilimbergo was exactly that, a place of commerce as well as a stronghold, grown thanks to the arrival of people from outside — Lombards, Tuscans and Jews — who made its population rise quickly. In 1284 count Walterpertoldo II had the Duomo begun, one of the finest Romanesque-Gothic buildings in Friuli, and in 1326, on the initiative of the counts Bregonia and Bartolomeo, the jurisdiction gave itself a body of laws of its own, the Statute of the Land of Spilimbergo.
The castle that gives the town its name — castrum de Spengenberg, after the Carinthian counts who settled there — was attacked and burned in 1511, during the war of the League of Cambrai, and then rebuilt in Renaissance forms. Inside it is the Palazzo Tadea, completed in 1566 by Tadea, widow of count Bernardino, who left it her own name. In those same decades Bernardino Partenio founded here an academy for the study of Latin, Greek and Hebrew, in a town where Jews had long since arrived. The vocation for worked stone has never stopped: in the twentieth century the Mosaic School of Friuli was born, named after Irene di Spilimbergo, and it brings students here from all over the world. The earthquake of 1976 devastated the city's historic and artistic heritage and cost one life.