Here is a series of remarkable windows from Chartres Cathedral in northern France. Please click on the image to enlarge it and have a closer look at its design.
These five lancets sit below the South Rose Window, and at first glance it is a very odd arrangement of figures. The central one is relatively conventional, showing the Virgin Mary with the Christ child, but the two windows flanking on each side are quite bizarre, in that they depict four smaller men sitting on the shoulders of four larger men. The ones above are holding on to the heads of the ones below, with their legs wrapped around their supporters’ necks, like some troupe of performing acrobats.
But this is not an entertainment, it is important symbolism, and it is quite an effective metaphor, once you understand who the characters represent. The four men below are the major prophets of the Old Testament, from left to right, Jeremiah, Isaiah, Ezekiel, and Daniel. Sitting on their shoulders, with haloes indicating that they are saints, are the four evangelists, the writers of the New Testament Gospels, again from left to right, St Luke, St Matthew, St John, and St Mark.
Symbolically, these figures are showing that the evangelical Gospels of the New Testament were built on top of the prophetic pillars of the Old Testament. The New did not supersede the Old, but together they define the law, linked by the pivotal figures of the Virgin Mother and the Christ child.

The evangelists Luke, Matthew, John, and Mark, sitting on the shoulders of the prophets Jeremiah, Isaiah, Ezekiel, and Daniel, with the Madonna and Child in the centre panel.
This beautiful set of windows date from about 1255, and they were paid for by the Duke of Brittany. The Duke’s blue and yellow check heraldry colours are at the bottom of the central lancet, below the Madonna and child, while the Duke himself and his wife and two children are depicted below the other four pairs of prophets and saints.
Not only did the Duke’s money and power achieve a form of immortality for himself and his family, this major donation probably earned them all some papal indulgencies as well, substantially shortening their post-mortem sojourn in purgatory.
Nowadays, of course, papal indulgencies can be acquired just by following the Pope’s tweets on Twitter. I’m not kidding.