The collection of around 5,700 libretti, which could be purchased in 1860 by the then Court- and State Library from the painter and gentleman of independent means Christian Her (1815-1892), is one of the world's largest libretto collections. Its comprehensiveness represents a unique source for the history of opera, literature and culture in the countries of the German language area from the 17th to the 19th century. In addition to around 4,900 books of opera texts (among them i.a. the libretto of the premiere of Mozart's 'Idomeneo'), the collection also comprises over 430 oratories and around 350 ballet libretti. From 2010-2013 the collection was catalogued and completely digitised according to national and international guidelines. The digital versions are available via the Libretto-Portal.