Another surprising feature of the plan is the thickness of the main body of the building ("corps de logis"), which consists of two rows of rooms running east and west. Traditionally, the middle of the "corps de logis" of French chateaux consisted of a single row of rooms. Double-thick "corps de logis" had already been used in "hôtels particuliers" in Paris, including Le Vau's Hôtel Tambonneau, but Vaux was the first chateau to incorporate this change. Even more unusual, the main rooms are all on the ground floor rather than the first floor (the traditional "piano nobile"). This accounts for the lack of a grand staircase or a gallery, standard elements of most contemporary chateaux. Also noteworthy are corridors in the basement and on the first floor, which run the length of house, providing privacy to the rooms they access. Up to the middle of the 17th century, corridors were essentially unknown. Another feature of the plan, the four pavilions, one at each corner of the building, is more conventional.