In modern societies, urbanization and large scale entertainment are obvious trends and consequently, large and complex multi-functional arenas are part of most large cities. The guidance of pedestrian flows in such buildings is a challenge. The Hermes research project, funded by the German Federal Ministry of Education and Research within the Security Research Program, aims to protect and save lives by developing an “evacuation assistant” that could allow stadiums and their venues hosting large events to be cleared quickly and more safely than currently possible. The Hermes system is designed to use information about a current situation to predict what will be the future positions of the occupants. It involves feeding data into a computer program about the availability of rescue routes, fire protection systems, and the distribution of people as determined using video cameras linked to image-processing software. This allows for flexible reactions to the actual situation for which usually no special emergency plans exist.