When Verdi's Don Carlo made its debut at La Scala in March 1868, it was hardly the latest operatic news; since its 1867 premiere at the Paris Opéra, it had been widely performed and written about. One aspect of the debates in the Milanese and the Italian press, however, deserves special attention: the depiction of the opera as a ‘monument’. Although the work's astonishing length (compared to that of most of Verdi's previous operas) and the composer's increasing prestige as a national figure might both have been reasons for this impression of monumentality, there were clearly others. The article explores some of these reasons in relation to post-Unification urban renewal, the increasing success of la musica dell'avvenire and the beginning of a slow rediscovery of ‘ancient’ musical works. It argues that Don Carlo was thought of as a monument primarily because it was perceived as standing between the past and the future, and as such was the epitome of contemporary attitudes towards these temporal categories.