In 2020, I decided to plan and carry out an experience: walking along the RER A line, to try and understand a region that has become invisible and to chart its scale and specific features. I propose designing a route from Marne-la-Vallée to Châtelet, for residents living along the RER A. This project has been designed as an evolution that moves from fantasy to reality. These days, we chart a local area using different tools such as kilometres and minutes... Can we perhaps imagine a new type of measurement, not connected to reason and calculation, but more sensitive and subjective? This would help us understand the local area in terms of our perceptions and “lived” time, which is subjective to each person.