In the second half of 2007 the Municipality of Milan decided to co-finance a one year project proposed by CILEA (Consorzio Interuniversitario Lombardo per l'Elaborazione Automatica) called “Biblioteca Aperta di Milano” (Milan Open Library) or BAMI, aimed at creating an integrated system to make a set of digitized documents from the cultural institutions of Milan available on the Web. To meet the goals of the project, we adopted Semantic Web standards and technologies to build the knowledge base and used a faceted browser for the user interface. Faceted browsing is an exploration technique for structured data sets based on facet theory which allows users to find information without a-priori knowledge of its schema. To store and provide the visualisation of digital documents we used CodeX[ml] and AriannaWeb. Regarding the selection of content, we decided to focus mainly on the documents that belong to a specific branch of the city's cultural heritage: those from the 19th century, giving special attention to musical documents. In this paper we present the methodology and the workflow that led us to build an ontology with the aid of a Scientific committee of librarians and 19th century music experts. We also illustrate the usage of a dedicated web-based editor that we used to populate the ontology. One of the most important objectives of the project was to overcome the limitations of the search engines traditionally used in the librarian domain (e.g. OPAC) by providing the users with new tools for browsing and analysing cultural knowledge. Thus, the paper also focuses on the BAMI User Interface, which was built by extending and enhancing Longwell, a faceted RDF browser developed by the Massachusetts Institute of Technology. We then describe the complementarity and flow of information between the three applications (Longwell, CodeX[ml] and AriannaWeb). The paper ends with a discussion of some possible evolutions of the project and of the main difficulties we encountered during the development.