Once in the Main Hall, walk straight ahead to the entrance of the Sully Wing. Take the escalator up, check your ticket, and then go along the hallway and around a rotunda. After twenty metres you will reach the Pavillon de l’Horloge. Walk until you face a wall. This is Room N°132. On the right side of the wall, there is a door leading to the medieval Louvre in Room N°133.