Lotario’s widow, Adelaide of Burgundy, took refuge in the fortress of Canossa (Canosso in the opera), to escape Berengario, who wanted to force her to marry his son Adelberto.

In Canossa, Adelaide was protected by Attone (Iroldo in the opera) but, unable to resist the siege by Berengario, she asked for the intervention of Otto the Great (Ottone in Italian), the “Holy Roman Emperor” of Germany, offering to be his wife if he granted her the royal rights due to her.

20th century and beyond Performances have included concert versions with Della Jones as Ottone and Eiddwen Harrhy as Adelaide given at London's Queen Elizabeth Hall in November 1978, and another at Usher Hall in Edinburgh on 19 August 2005[2] with the Scottish Chamber Orchestra and Chorus with Jennifer Larmore as Ottone and Majella Cullagh as Adelaide.

The Festival della Valle d'Itria in Martina Franca in Italy presented staged performances in August 1984, with Ottone sung by Martine Dupuy and Adelaide by Mariella Devia.

In addition, the Rossini Opera Festival staged it in Pesaro in August 2006, with Daniela Barcellona and Patrizia Ciofi singing the roles of Ottone and Adelaide respectively[3] and it was presented again in a new production in 2011, also with Barcellona as well as Jessica Pratt in the title role.