AZIMUT is a mobile robotic platform that combines wheels, legs and tracks to move in three-dimensional environments. Its design is the result of an interdisciplinary effort combining expertise in mechanical engineering, electrical engineering, computer engineering and industrial design. After presenting AZIMUT, this paper describes the challenges of designing such a robot, outlining the interdependencies between the disciplines and the difficult compromises that have to be made during the iterative design process of a mobile robotic platform. Modularity at the structural, hardware and embedded software levels, all considered concurrently in an iterative design process, reveals to be key in the design of sophisticated mobile robotic platforms.