In order to help researchers of humanities study the cultural ancient resources from temporal and geographical perspectives, we build WebGIS-RBDL at Peking University. In WebGIS-RBDL, metadata records and historical map layers are linked together, and therefore users can get more spatio-temporal information about rare books through folded map layers, including historical maps, modern maps and landform images. In this paper, the architecture of WebGIS-RBDL is introduced. Then, the principles, rules and methods for metadata extracting and correlating in WebGIS-RBDL are discussed. Furthermore, efficient tools to extract spatio-temporal information automatically from rare-book metadata are developed. The WebGIS-RBDL can be extended to include other ancient collections easily. Our efforts show that using GIS in digital libraries is a new and promising method to build more effective user-friendly interfaces in digital libraries.