The line leaves Gare Montparnasse to cross Paris's southern suburbs, partly under the Coulée Verte. This is a tunnel above which footpaths and recreational areas have been created, to reduce the effect of the LGV running through the area. The line at this point follows the route of the former railway line from Paris to Chartres. TGVs coming from the north or southeast of France via the LGV Interconnexion Est join the line at Massy. After the new Massy TGV station, the line passes through the Villejust tunnel and then follows the A10 motorway. Near the Saint-Arnoulttoll plaza, the LGV turns south and leaves the motorway. The line then follows the ligne classique from Paris to Vendôme until the junction at Courtalain.