Reredos (or You Learn a New Word Every Day) – Heinz Memorial Chapel, University of Pittsburgh, Pennsylvania

Reredos = An ornamental facing or screen of stone or wood covering the wall at the back of an altar, frequently of ornate design, with niches, statues, and other decorations. The word was common during the 15th century, rare in the 16th, and from about 1550 appears to have been practically obsolete until revived in the 19th century.

- Oxford English Dictionary