The paper describes work carried out as part of the GUIDE project at Lancaster University. The overall aim of the project is to develop a context-sensitive tourist guide for visitors to the city of Lancaster. Visitors are equipped with portable GUIDE units which in turn provide interactive services and dynamically tailored Web based information, reflecting the visitor's preferences and environmental context. In contrast to existing tourist systems, all information in GUIDE is obtained dynamically using a city-wide wireless network infrastructure. We focus on the design of the GUIDE information model. The model presented is novel by virtue of the fact that it enables both geographic and contextual information to be captured. The paper also describes our development of an efficient broadcast mechanism which enables visitors' requests for information to be serviced quickly despite the wireless communications infrastructure employed.