Describe a specific architectural detail from St. John the Divine. It can be anything you choose—for example, a sculpture on the main façade, a flying buttress, or a floor tile. Create a drawing of this detail, then provide a detailed written description of your chosen element, explaining how it relates to the building as a whole. Questions you might discuss include, but are no means limited to: What is your chosen detail's structural role? What is its visual role? What materials were used? Does the detail's form reflect its function? Does it work as part of an integrated whole, or stand out?

From the main seating area of St. John the Divine, one can ascend on the far left or right a handful of gentle steps to a walkway connecting the main chapel with several smaller ones. The ambulatory extends first straight ahead, then curves in a half-circle to double back along the opposite side, a layout mimicking horizontally the myriad vertical arches found in this space. One such arch can be found near the ambulatory's left terminus, just past the stairs, seemingly emphasizing the border between two sections of the structure. On the ground, centered directly underneath this arch, is what appears on first glance to be a welcome mat.

It could very well have been one. Given the ongoing construction on the cathedral, it would not have been altogether implausible for guests to be asked to wipe their feet from time to time. A closer look, however, reveals that the figuration is integrated into the floor.

Geometrically, the “welcome mat” consists of a series of five concentric rectangles. At center is a slab of white marble with streaks of dark blue and red. Laid around it are square tiles, seven along the short edge, ten long. The tiles are blue, with an inlaid red design of a bulbous red X. (It was these tiles that initially caught my eye, which sought to discern the precise shape of the X.) Around these tiles is a ring of black marble. Next is another series of composite tiles, 5×9 this time, maintaining the fourfold symmetry of the previous set: four diamonds, their tips touching the edge of the tile and each other, a squares in each of the four triangles of space along the diamond's sides. Finally, stretching to the wall, is a mass of gray stone.

The patterns in the tiles hint at patterns in the larger structure. Sure enough, there are some. The stone and tile sections alternate, with muted stone as an anchor and strikingly bright stone at center, enveloping the whole from without and within, perhaps intended as a testament to God's omnipresence. The natural materials contrast strongly with the man-made: whereas the former are large, streaked irregularly, and expensive, the latter are small, orderly, and more than a little tawdry in appearance, as if to emphasize the feebleness of human endeavor as compared with the grandeur of the Lord.

Why does this “welcome mat” need to be there? The stairs and the arch already underscore the separateness of the two sections of building. Arguably even the arch is superfluous in conveying the message. But the gigantic, ornate building is clearly not designed to say much with little. It would be strange, indeed, to find this spot of floor unadorned.