MERCURE PARIS LA DEFENSE ARCHE. Take line A3 OR A4, station NANTERRE PARC, direction PARIS NORD. From the Périphérique Ouest, take the La Défense/Porte Maillot exit then take the Boulevard de La Défense and head toward Nanterre Parc. At the second set of lights, turn left and follow signs for the Mercure. From the A86, exit at Nanterre and head towar d Nanterre Parc. At the lights, turn right and you will see the hotel car park. From the A14, head toward Nanterre Parc, then follow the instructions above. By RER: on line A, alight at Nanterre Préfecture. The hotel is at the exit to the RER station.