A long-lost portrait of Theodor Mommsen has been found in Geneva/Peron among the possessions of one of the descendants of the family. The bust was made by Reinhold Begas in 1887 on the occasion of Mommsen’s 70th birthday. Although Begas was one of the most notable artists of his time, Mommsen, vigorously disapproving of the portrait as an ‘anticipated infernal torture’, buried it in his private home. The article investigates the reasons for Mommsen’s harsh refusal and finds them in the latter’s personal and political attitude, not in the aesthetic quality of the work of art. In fact, it is evident that the bust, forgoing worn out conventions, shows us Mommsen’s difficult character in a difficult period of his life.