From the Gothic period onward, both in Europe and elsewhere, altarpieces in churches and cathedrals were often in triptych form. One such cathedral with an altarpiece triptych is Llandaff Cathedral. The Cathedral of Our Lady in Antwerp, Belgium, contains two examples by Rubens, and Notre Dame de Paris is another example of the use of triptych in architecture. The form is echoed by the structure of many ecclesiastical stained glass windows.