Views of the High Altar of the Basilica of Sant'Apollinare in Classe

The Basilica of Sant'Apollinare in Classe is one of the most venerable ancient basilicas in all of Christendom, justly celebrated for its mosaics and as an exemplar of early Christian architecture. Now examples of early Christian basilicas invariably include the presence of a ciborium, which is to say, the architectural canopy that covers the freestanding altar. This is a feature I have frequently spoken on frequently over the years. Here is what the Catholic Encyclopedia says about it:
From the fourth century altars were, in many instances, covered by a canopy supported on four columns, which not only formed a protection against possible accidents, but in a greater degree served as an architectural feature of importance. This canopy was known as the ciborium or tegurium... the dignified and beautifully ornamented ciborium as the central point of the basilica, where all religious functions were performed, was an artistic necessity. The altar of the basilica was simple in the extreme, and, consequently, in itself too small and insignificant to form a centre which would be in keeping with the remainder of the sacred edifice. The ciborium admirably met this requirement.
My selection of this particular quotation is quite purposeful, for whenever I look at Sant'Apollinare as it stands today, as brilliant and awe inspiring as it is, it's high altar certainly seems to cry out for the presence of this ancient and noble feature.

I found myself wondering then, did Sant'Apollinare historically have a ciborium?  I would find it difficult to imagine that it did not admittedly, and while I am yet researching the particular question of this basilica in its earliest forms, I did turn up some interesting photographs and engravings of the basilica from the mid-19th century which show the high altar covered with a ciborium -- one that would appear to be of baroque vintage.:

It would seem that it was at some point in the later 19th century or early 20th century that this was either removed or destroyed. Here is an image of the basilica as it stood at that period and as it essentially still stands today:

Whatever the case in the history of this particular basilica, it brings to mind the fundamental importance, utility and desirability of the ciborium where freestanding altars are concerned, serving both as a means to focus one's attention on the altar and lending the altar an architectural magnificence that it might not otherwise have.