Currently, modelling of knowledge and skills in a MOOC and the associated instructional and pedagogical engineering process is a major challenge in order to support designers and facilitate learning. This article explains how visuo-cognitive metaphors of the "metro map" and "travel" make possible the design of connections between the representation of knowledge and learning. The researcher can measure this approach in a double movement: topography to topology (from visual-spatial experience to cognitive change) and topology to topography (from metaphor to artifact design). Our reflections focus first on the application of Lakoff and Johnson's conceptual metaphor theory in learning, as well as on the contributions of the Loci method on cognition. These theories and the results of previous work have shown the interest of the metro map metaphor in the Computer Environment for Human Learning (EIAH in French), which we have implemented in our MetroTeach model with the Design-Based Research method. Recent studies have revealed a heterogeneity of MOOC devices and a lack of application of instructional engineering principles. We therefore pose these questions again by proposing a model of the MetroTeach system. This will allow us to rethink the ontological dimensions of MOOCs and their legitimate status as a research object.