The King's Staircase

This space is known as the King's Staircase. Louis XV originally had it built so he could go straight up to the attic rooms above, but Marie Antoinette later had the staircase removed and replaced it with a special mechanism instead. The black fixtures visible on either side of the window and door are what remains of that device. One floor up, in the Movable Mirror Room, this very mechanism was used to raise and lower the mirrors.