Elsewhere on this blog we have posted reconstructions of Cluny III and the original St. Peter's basilica. Here is the best video reconstruction of Cluny III that the Rad Trad has yet seen. As a note of interest, the image of Christ enthroned in the apse is very reliable. The same image graced the apse of the original St. Peter's and was copied by the pro-papacy Cluniac monks, who in turn copied the image in the apse of the chapel of the abbot's still extant retreat house. Cluny III was once the largest church in the world, larger than either the old St. Peter's or St. Paul outside the Wall. At one point Cluny housed over four hundred monks, but their rapid expansion during the reform papacies of the middle ages and the proliferation of more penitential monastic orders trimmed Cluny's numbers. When the church was destroyed during the time of the French Revolution, there were under a hundred monks in this impressive church.
The church itself was an interesting example of architecture in transition from the ancient Roman style into the medieval style. We see nascent arches, too round to be gothic, but too bold and dark to be Roman. There is a divider between the nave and choir, anticipating the Rood screen and succeeding the altar ciboria of the Roman basilicas. There is the long, narrow choir, clearly indicative of the emerging choir praxis that survived until the 1960s and which replaced the almost Byzantine existing praxis wherein the non-celebrating district subdeacons and deacons and full-time cantors would sing the proper chants from lecturns in the Roman churches. And above all, the Roman basilicas reflected the Roman approach to public gatherings: large, broad, and with an elevated place for those in authority—in this case, the Pope. In Cluny III, we instead find tall, narrow structure reflecting the dynamic between heaven and earth and a direct focus on the altar created by the preceding features and the small opening in the screen. Architecture was becoming more and more focused on the action of God.
What a place it must have been!