In this paper, we provide results from the design-based research and development process of a digital didactical tool: mathematical maps. We describe in detail the current research cycle, in which the mathematical maps are integrated into a geometry course designed cooperatively by university mathematics teachers and researchers in mathematics education from different universities. The results of the evaluation affirm the (perceived) usefulness of individual functionalities of the digital tool but also point to suggestions for design improvement. Furthermore, the use of the map within the geometry course seems to promote favorable beliefs regarding the nature of mathematics.