LSV is located at the ground floor of the left wing of the d'Alembert building at ENS Paris-Saclay. See also the access page for ENS Paris-Saclay.
To reach the ENS Paris-Saclay take the city train RER B and stop at the station Bagneux. Then you can follow the path drawn on the map (avoid to get off at Arcueil-Cachan station as you would have to walk 10 min more). The train is direct, but not all trains stop at Bagneux. Therefore check that the sign Bagneux is alight. The trip takes approximately: