We discuss the user study of a mobile cultural heritage game designed to stimulate reflection about a city's history. Aided by location-aware technology, the game fosters the serendipitous discovery of points of interest, historical images and stories, whilst players wander the city. This exploration differs from the typical precalculated path recommendations used by other location-based applications. It triggers reflection about the city's past that is as unique as its visitors. Ours is one of the first studies to attempt an understanding of the effects of serendipitous urban discovery and historic reflection-triggering technologies on user experience. We combined field trials with controlled experiments, analysing perceptions of the experience and value using responses expressed in open-ended questionnaire items. Using thematic coding and sentiment analysis, we observed types of emotional responses, indicating four potential profiles of their likelihood towards future technology adoption. Enthusiastic and Interested users appreciated the freedom of movement choice that created an autonomous experience that fostered a sense of personal accomplishment. The interface interactions of the game, designed to stimulate reflection, supported a feeling of connectedness to others. In contrast, Cynical and Sceptical users were less tolerant of perceived technological issues, requiring more perfection in functionality and design. These users are less likely to be the early adopters of serendipitous location-based apps. The game was developed as part of a large cultural informatics project but, unlike typical evaluations, we conducted this study midway through the project and not at its end. This approach (1) gave the team the possibility to take stock, pause, and reflect and (2) provided insight on future design improvements for increasing the perceived value of serendipitous urban discovery applications. Our results contribute towards a grounded understanding of user experience and help progress the development of cultural heritage applications that incorporate elements of reflection and/or place-based exploration into their functionalities. CCS Concepts: • Human-centered computing → Empirical studies in ubiquitous and mobile computing;