The Projektgruppe Mobile Informationssysteme (ProMIS) is an educational research and development work group that aims at developing concepts and solutions for the application of mobile visitor guides in museums and cultural heritage sites. Hand-held computers like personal digital assistants (PDAs) with touch screens and headphones offer specific advantages over conventional models of delivering visitor information: they are always on-hand and can provide sound as well as pictures and animated movies. The skilled combination of audio and visual information, complementing each other, is capable of enhancing the visitor?s experience. Our presentation introduces a running project that quite clearly shows the benefits of the use of PDAs in cultural heritage sites. We discuss part of a guided tour that deals with the treasury of the Halberstadt Cathedral, focussing on a complex object: the mighty reliquary shrine of the bishop?s church.