But the Misericordia structure may well be unique among charity loggias in a most important way: rather than an extended series of arcuated compartments, it comprises a single bay only that is crowned by a hemispherical groin vault, hence its approximation to a domed space.
Here it is of capital importance to note that arched and domical constructions of these sorts evidently carried identical connotations, for both "arch" and "dome"--and "vault" as well, of course--belong under the rubric of arcuated structures.
A very early instance of the arcuated canopy in such a context, showing Christ's entombment, appears in the middle of the right apron of the painted cross known as Uffizi number 432, a work of the late twelfth century.
Equally influential was the original arcuated structure of a few years later marking the tomb of Saint Peter, also described previously, which from the beginning was physically associated with the high altar of Old Saint Peter's, although exactly how is disputed.
They differ in that the Saint Donatus shrine lacks a canopy, and also in that it does not depend on arcuated forms except in a secondary way (the sculptures of the upper registers are framed by arched moldings).
But several occasions exist in fourteenth-century Italian monumental art where an arcuated aedicule must be interpreted in a fully three-fold manner, as marking a tomb, an altar, and a throne simultaneously.