This artcle describes work done with enterprise architecture of the National Digital Library. The National Digital Library is an initiative of the Finnish Ministry of Education and Culture. Its purpose is to promote the availability of the digital information resources of archives, libraries and museums, and to develope the long-term preservation of digital cultural heritage materials. Enterprise architectures are a tool for strategic management and planning. An enterprise architecture also functions as an aid at a more practical level. It shows, for example, what kind of changes and improvements may be made in one system without overlap or conflict with other systems.