That’s the shadow of the top of the big stella cometa (Christmas star) cast onto the marble steps/seats of L’Arena.
I like the curve of the shadow and the curve of the steps. Of course, i did flip photo upside down, but I don’t think that’s initially obvious. Unless you took note of the shadow in the previous photo. (This is NOT actually just a piece of the previous photo; this photo is a one I took just of the shadow with the intention of flipping it).