After plenty of searching, FI and I kept coming back to this venue: The Odescalchi Castle in Bracciano, near Rome. This is most likely the venue we'll be going with. All we have to do is contact them about one day exclusive use and schedule a visit. I hope it works out and goes as planned.
Here are some photos of the location(obviously, I didn't take these pics myself lol):
This is the castle itself:
This is the entrance first entrance leading to the side (the red carpet is optional, but we want it):
This is the second entrance on the side that'll lead the guests inside:
I'm not sure which room would hold the ceremony yet, but this is where the pre-dinner cocktail would be; the first garden overlooking the lake:
And this is where the reception would be held; the courtyard. Centerpieces, table decor, etc. would be changed though. The castle offers fireworks during/after the reception above and in this area: