The Historical Archive plays a key role in the heritage of the Basso Foundation and has done since its inception. It is regularly open to the public and houses collections declared to be of historical interest by the Archival Superintendency of Lazio.

The historical archives currently contain 60 collections, which include all Basso’s papers concerning his political and cultural activities, papers related to early twentieth century socialism and anarchism, papers on Christian social movements, documentation related to Italian and international politics, documentation on movements of the sixties and seventies, and editorial archives. Completing the archival heritage of the Foundation are collections made up of papers on Basso’s international activities and work for peoples’ rights, conducted through the Russell Tribunal and the Lelio Basso International Foundation for the rights and liberation of peoples.

Also of interest are the institutional repositories of the Issoco and the Foundation, and the documentary collections of the latter, which include manuscripts from the time of the French Revolution, a section on the first and second international, papers belonging to exponents of German and Russian social democracy and correspondence between Bogdanov and Gorky.