The characteristics of a smartwatch impose several challenges regardig the design of a pedestrian navigation aid. This paper illustrates how landmark-based pedestrian navigation systems for smartwatches can be developed, considering the small screen sizes as well as the very limited interaction capacities of these wrist-worn devices. Particularly, by the use of a user-centred design approach, an initial user interface was developed, tested, and refined in two field experiments to create a final user interface. A combination of map view and direction view was proposed, where the map view provides an overview of the environment and route, while the direction view gives clear instructions (turning information) for decision points. The interface was further enhanced by the use of vibrations before decision points. In addition, landmarks were carefully considered and incorporated into both map view and direction view. The field experiments showed that these key features of the revised interface can effectively support pedestrian navigation via smartwatches.