We designed and implemented a digital library system that supports content-based retrieval of multimedia objects based on MPEG-7 and XQuery. MPEG-7, a metadata standard for multimedia objects, can describe various features such as color histograms of images and content descriptors. As such, a multimedia digital library system built with MPEG-7 metadata can provide content-based search for multimedia objects. Since MPEG-7 is defined by XML schema, XQuery is a natural choice as a query language. By adopting the standards, MPEG-7 and XQuery, our system has benefited for interoperability. First, any MPEG-7 metadata instance can be accommodated into the system with no additional effort. Second, any system that can generate a query in XQuery can retrieve necessary information. Third, our system can be easily extended to support any XML documents. Currently we have developed a prototype system for retrieving images of Korean cultural heritage.