Tambour (drum)

A cylindrical piece of stone; tall and big colonnes (columns) are often not hewn out of one piece of stone, but composed of a number of drums.
The picture clearly shows the drums forming the contrefort-colonne (buttress column).
Tambour also has a second meaning; it can also be the circular or polygonal wall on which a dôme (dome) rests.

Notre-Dame-de-l'Assomption - La Chapelle-sous-Brancion