In the area of the Villa there are two treasure chests indicated on the map, as so:
This screenshot was taken while I was on the stairs to the underground sanctuary, and the map items are lit up, which usually indicates they're at the same elevation as myself and so I presume they must be underground? Having looked, they don't seem to be in the building, or on the roof, so I'm pretty sure they must be under there somewhere.
I'm sure it's completely unnecessary to get them, but I tried looking for them and couldn't find them, and now I'm annoyed. So, how do I get to them?