This paper discusses a research-in-progress project engaging citizens in the collaborative 3D reconstruction of special urban features (SUFs) – visual works of art located in urban public spaces. While most artists modelling urban public spaces use basic 3D building models, these models do not include visual artworks. Because urban planners use artists’ models when designing urban public spaces, we believe it is necessary to incorporate SUFs into 3D city models to help urban planners and artists visualize urban spaces more effectively. To achieve this goal, we propose a bottom-up approach to the geographic visualization of SUF cultural assets (i.e. cultural mapping) which so far has not been undertaken as a citizen science project. The main aims of this project are to engage citizens in contributing to 3D SUF models and to familiarize them with citizen science. The method includes crowdsourcing SUF data and analysing it using ‘structure from motion’ (SfM) algorithms. After a 6-month campaign in Lublin, Poland, this project has so far resulted in 271 observations and 144 collaborative 3D models, creating a 3D open-data product which can be used for further culturally sensitive urban planning purposes.