For 10 points, name this Italian castle that became a key symbol of the investiture controversy in the 11th century.
This estate was passed down to a woman raised by Arduino della Padule, who fortified it with structures named Montezane and Montelucio. It was given to Matilda of Tuscany, who fought against a man who had earlier visited this place at the Battle of Volta Mantovana. A key meeting at this estate was prompted after the issuance of Dictatus Papae. It was here where one man wore a hairshirt for three days after he had crossed the Alps. After those three days in the snow, Pope Gregory VII lifted his excommunication of Holy Roman Emperor Henry IV.  For 10 points, name this Italian castle that became a key symbol of the investiture controversy in the 11th century.
This estate was passed down to a woman raised by Arduino della Padule, who fortified it with structures named Montezane and Montelucio.
Canossa