During the last few years numerous multimedia archives have made extensive use of digitized storage and annotation technologies. Still, the development of single points of access, providing common and uniform access to their data, despite the efforts and accomplishments of standardization organizations, has remained an open issue, as it involves the integration of various large scale heterogeneous and heterolingual systems. In this paper, we describe a mediator system that achieves architectural integration through an extended 3-tier architecture and content integration through semantic modeling. The described system has successfully integrated five multimedia archives, quite different in nature and content from each other, while also providing for easy and scalable inclusion of more archives in the future.