The Progetto Lombardo Archivi in Internet (PLAIN) aims at preparing an environment that alllows an easy access by users to the wide heritage of descriptions, already existing in electronic format, of historical archives preserved in the region. The project is being developed under the coordination of the Pavia University, on the basis of a covenant with the Lombardia Region (in which also the State Archive of Milan is represented). It’s included within the wider project Archivi storici sul Web, for which the Lombardia Region and the State Archive of Milan collaborate in the context of the Framework Program Agreement about the cultural heritage field.