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 was a natural choice as a query language. By adapting 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 an 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.