Over the last few years, the use of mobile technologies has brought the formulation of location-based learning approaches shaping new or enhanced educational activities. Involving teachers in the design of these activities is important because the designs need to be aligned with the requirements of the specific educational settings. Yet analysing the implementation of the activities with students is also critical, not only for assessment purposes but also for enabling the identification of learning design elements that should be revised and improved. This paper studies a case that applies visualizations to support students' self-assessment and teachers' inquiry of a mobile learning design. The design is a gamified location-based learning activity composed by geolocated questions and implemented with the "QuesTInSitu: The Game" mobile application. The activity was designed by seven teachers and enacted by 81 secondary education students organized in a total of 23 groups. Log files, gathered from "QuesTInSitu: The Game," provided the data for the visualizations, which represented relevant aspects of the group activity enactment (both time used to answer questions and to reach the geographical zone of the questions, scores obtained per zone, etc). On the one hand, the visualizations were discussed with the teachers as a learning analytics tool potentially useful to consider when redesigning the activity, if needed. On the other hand, the study shows that the visualizations led students to make a better diagnosis of their own activity performance.