This preprint corresponds to the author’s submitted manuscript version. The manuscript has not yet undergone peer review. A revised version of this article is currently under review in Journal of Maps. If accepted, the final published version will be available via Taylor & Francis. Please cite this work as a preprint until the final version becomes available. This study explores how the built environment influences children’s physical activity during school travel and within school neighborhoods in Olomouc, Czechia. A unique dataset combines accelerometer-measured activity, manually mapped school routes, and detailed GIS-based environmental indicators. Data from 161 eighth-grade pupils across ten primary schools were analyzed using 25 m buffers along routes and 500 m network service areas around schools. Environmental variables included building heights, pedestrian infrastructure, traffic intensity, greenery, noise, and traffic accidents. Results show that active school travel is positively associated with sidewalk area, traffic intensity, and building height, but also with traffic accidents — revealing both accessibility benefits and exposure risks in compact urban settings. Total daily activity and sleep were not significantly related to environmental factors. The study demonstrated that the built environment strongly shapes active school mobility, while overall activity patterns depend mainly on individual and social routines. The integration of ActiGraph accelerometer and spatial data offers an innovative method of analyzing children’s mobility in medium-sized European cities.