Fifteen teenagers from different neighborhoods and institutes, led by teachers of the Association “Matematici per città”, crossed Naples living classes in the parks, squares, unexpected spaces of the city that has turned into a magnificent open-air classroom. The educational path described was carried out during the time in which the schools were closed and was exactly a response to the indefinite closure of the Campania school in the COVID 19 pandemic time. The article describes and analyzes the activities carried out, placed in the field of Mathematical Informal Education and the project is read through the lens of functional linguistics, even if there are different theoretical frameworks in the background of a complex and rich path such as that of the Infernal tombola.