In an intensive workshop from November 11th to November 18th 2002, five teams consisting of members of architectural offices, artists, planners, developers, citizens & students came forward with a series of ideas & designs at urban & landscape level for Trekroner “˜st, a new neighbourhood in Roskilde, Denmark.. 3dkroner.dk1, an interactive, web based 4D public participation tool (PPT) was created and used for communicating the workshopis results to a broader public on the one hand, and to start a two way communication process between planners and citizens on the other hand. In this paper I will rather describe the toolis development, its implementation in the workshop and the experiences the project team made from this process than discuss public participation tools in general