That is a great piece of information t to include about St. Peter's request to be crucified upside down because he was not worthy to be crucified like Jesus.

I understand the piece was commissioned by King Ferdinand and Queen Isabella of Spain, but why did they commission it?

I find it fascinating that the Tempietto is built on the posthole of St. Peter's Cross. I actually find it fascinating that monuments like this and many others, like churches serve as focal points for bible events. It helps me make these events more tangible and still maintain their idealistic integrity. Helps me believe events like the crucifixion really happened.