At the bottom of the yard 62 rue du Cardinal Lemoine( former rue des Fossés St Victor), you can see a piece of the wall of over a hundred meters long meters whose "chemin de ronde" has been transformed into a public path. You can access this path from 47 rue Descartes. you need to walk up to the 1st floor to access the top of the wall. Unfortunatelu many many noisy tourists have lead the owners to install a digicode in order to limit the access to the building.