I would have to say that in my opinion St. Peter's in Rome takes the prize as "Most Photogenic Interior." I have been looking at my photo collection, and I have a disproportionate number of the inside of this awe inspiring structure. There is so much to look at, I wonder if paying attention to the Mass would be secondary? I do know that one of the Calvinist reactions against Catholicism concerned adornment. Compare this sparse interior in a Calvinist church in England.
I like this view of the interior of the dome because you can clearly see the Latin Bible verse which came to be known as "The Petrine Doctrine." Peter became the first Pope in a 2000 year succession of Popes.
"Tu es Petrus et super hanc petram aedificabo ecclesiam mean et tibi dabo claves regni caelorum" ("You are Peter and upon this rock I will build my Church, to you I will give the keys of the kingdom of heaven." Mt 16:18)
Jesus may have been making a little joke when he said this to Peter because "Peter" was derived from the Greek word for "rock." Was Jesus smiling when he said this? I ask this because in the Middle Ages there was actually a theological debate about whether Jesus ever laughed, since there is no specific documentation of this in the New Testatament.