This paper describes the design and implementation of an interactive walk-through of a reconstructed German stronghold, the Dillenburg. The application is currently in use at the local museum. Applying technologies and algorithms primarily used for the development of realistic 3D computer games, we present a system that can be categorized as a Serious Gaming environment, a term that has recently come into existence. More specifically, it can be called a Cultural Heritage Game. With this paper we want to give a programmer’s view on the topic of interactive cultural heritage systems.