What was “Canossa” (1077) famous for?

The story behind the answer

In 1077, amid the Investiture Controversy, King (later Emperor) Henry IV crossed the Alps to the castle of Canossa, where Pope Gregory VII was staying with Matilda of Tuscany. Excommunicated and facing revolt, Henry performed public penance—reportedly barefoot in the snow and wearing a hairshirt—for three days until Gregory lifted the ban.

The scene became a defining symbol of papal authority over secular rulers in the high Middle Ages. Although the truce was brief—Henry later marched on Italy and backed an antipope—the episode crystallized the stakes of church reform and royal power. The conflict over lay investiture continued until the Concordat of Worms (1122), but “to go to Canossa” still evokes a ruler’s dramatic submission to ecclesiastical judgment.