In Switzerland, the largest railway stations are called RailCities by the Swiss Railways. It emphasizes their transformation into places to perform different activities, similar to a small-scale city. Concerns are similar than in urban areas: costs of new infrastructure, traffic congestion, land scarcity. The activity-based approach models the activity participation patterns. Traveling is seen as a derived demand from the need to pursue activities. In the pedestrian context, postulate rules, such as the home-based structure with tours from home, do not hold. The large dimensionality of the problem implies aggregation or hierarchy of dimensions, with priorities of activity types. We develop a modeling framework based on path choice. The activity-episode sequence is seen as a path in an activity network. The sequence is not home-based nor tour-based. The model can be applied in different contexts, both urban and pedestrian. The large dimensionality is managed through an importance sampling based on Metropolis-Hastings algorithm for the generation of the choice set. The time is discretized. The utility of an activity-episode sequence is the sum of individual trips and activities, including the time-of-day preferences and the satiation effects. First results of a case study on campus are presented, based on data from WiFi traces.