By the end of this year visitors to the Flemish town of Mechelen can discover the city with the help of the new CityInMyPocket walking guide. Instead of following a person or a book, people can pick up a CityInMyPocket digital walking guide and go sightseeing at their own speed. So, leave your heavy guide books and many flyers at home. CityInMyPocket will tell you just as much, and even more. CityInMyPocket is like having a friend who lives in the neighbourhood showing you around. The goals are formulated, but how did we manage? In order to succeed, we started investigating how people usually visit a city. Are people just strolling around the city or do they strictly follow the walk mentioned in their walking guide? What are the information needs during their stay? In parallel with the user analysis, we looked at similar projects and applications to see how they approached the problem. Based on the results of the user needs and the tests of existing applications, we defined the concepts of the CityInMyPocket walking guide. Here, we can distinguish three main building blocks: the map application, the search engine and the route planner. When the overall concept was ready and the information needs where specified, we started building the information model based on the Topic Map standard. For the map information we explored the power of the SVG standard. The moment the first data set was prepared, we implemented the map application. The remaining concepts were built around the central map application. This paper describes in more detail how we managed to build the CityInMyPocket walking guide.