The work reported here takes place in the educational domain. Learning with Computer-Based Learning Environments changes habits, especially for teachers. In this paper, we wish to demonstrate through examples how learning sessions set up in a Game-Based Learning environment may be regulated thanks to observation facilities. Providing teachers with feedback (via observation) on the ongoing activity is thus central to being aware of what is happening in the classroom, in order to react in an appropriate way and to adapt a given pedagogical scenario. The first part deals with the description of our view of learning games illustrated through the “pedagogical dungeon”: a game-based environment that we have developed. The second part of the paper focuses on the description of different ways and means to obtain information about the learning activities. It is based on traces left by users in their collaborative activities. The information existing in these traces is rich but the quantity of traces is huge and very often incomplete. Furthermore, the information is not always at the right level of abstraction. That is why we explain the observation process, the advantages of a multi-source approach and the need for visualisation linked to the traces. In the third part, we illustrate these concepts in the pedagogical dungeon equipped for observation and with the capacity for collaboration in certain activities. We pay particular attention to the regulation process of the collaborative activity by providing case studies explaining how the observation process enables the regulation actions. Finally, the feedback about the experiments presented is discussed at the end of the paper.