Final answer:
A ciborium is an ornamental canopy of stone or marble set over an altar in a church, often seen in Christian religious architecture and adorned with elements like marble revetment and mosaics to create a divine atmosphere.
Step-by-step explanation:
An ornamental canopy of stone or marble permanently placed over the altar in a church is known as a ciborium. Typically found in Christian churches, the ciborium stands as a monumental feature, invariably adorned and crafted to reflect the artistic and spiritual ambitions of the period. In examples like Justinian's Hagia Sophia, the marble revetment would often be applied, presenting a grand and luxurious appearance as described in the references to Byzantine architecture. The effect of the golden mosaics and the light filtering through illustrates the ethereal quality and the importance of such elements in creating a divine atmosphere within the sacred space of the church.