Go down on Vernet street. On the square, take the Etats Généraux street, 100m turn left on Noailles street and follow the GR11 marked white and red till the ONF Forest House located after the railway bridge.
From this point, follow the yellow marked PR route, shared with the GR11
After passing under the bridge take the 1st right for a few meters, leave the GR11 and continue the yellow PR towards the two water towers.
Pass under the N286 and turn left on a path in the woods till the Clément Ader monument.
Cross the D91 and continue on a path more or less close to the railway line.
At the edge of the Bois de Satory, take the forest path (south) till the Porte du Bois Robert.
At the crossroads, turn right onto the GR11 diverticulum and continue to Saint Cyr l'Ecole.
Arrival at Saint-Cyr l'école (Train Station -line N Paris-Montparnasse/Rambouillet)