Aware of the consequences of their inactive lifestyles, many people still struggle to integrate enough physical activity into their busy lives. Interventions that nudge to reinforce existing active behaviour seem therefore more likely to be effective than those adding an activity to daily routines. To encourage people to increase their physical activity level, we designed Discov, a network of physical waypoints triggering people to lengthen their walks. Placed in a public park, Discov encourages people to explore their surroundings in a fun and challenging way by creating an interactive walking experience. Adopting a Research-through-Design approach, we explore the potential of the design of accessible infrastructures and human-environment interactions to impact public health by nudging citizens into being more physically active. We discuss insights gathered through this process and report on first user tests of this interactive walking experience.