National Immovable Cultural Heritage Inventory System (Tescilli Kultur Varliklari Tasinmaz Ulusal Envanter Sistemi / TUES) is a centralized web-based GIS system, which is capable of cross-querying 10,000 protected areas (archaeological, urban or historical), 100,000 monuments and registered historical buildings, more than 500,000 Conservation Council decisions and nearly 20 million pages of archival documents for all provinces of Turkey. In one word, aim of this project is inventorying of immovable cultural heritage of Turkey on a web-based GIS system for Ministry of Culture and Tourism and other national governmental agencies. This system is also important for Turkish National GIS Project called TUCBS (Turkish National GIS); the mainframe of all GIS based e-government projects. In this paper, we're going to analyse the necessity of centralized Web/GIS based inventory system for cultural heritage, agriculture, stockbreeding, mining industry and many more sectors; and then we're going to discuss main design elements and modules of the application.