Area not visible

Your italian area is a closed way tagged with "area=yes" + "name=castello" which means "castle" in English. Based on Bing aerial imagery, your polygon seems to be the outer line of an historic castle. It this is the case, you just have to tag it with "building=yes" (or building=castle) + "historic=castle" + "name=Castello".
But if you do this, you will see a huge single block where in reality, there is a courtyard inside. To fix this, you will have to create a multipolygon relation with your "area" as outer ring and a new closed way representing the courtyard added in the relation with an "inner" role. Then, if you wish, you can move all tags from the outer ring (your current "area") to the multipolygon relation ("building" + "historic" + "name").

And with these tags, you don't need an "area=yes" tag because it is always the case for buildings. Basically, the tag "area=yes" is mainly used for "highway's" on closed ways only to determine if it's representing a loop (like a race track) or an uniform surface/area (area=yes).

The use of the area needs to be designated, you've just defined an area without defining it's purpose. Could it be landuse=residential? The area tag would then be redundant and should be removed. I think the name of the area ought to be capitalised as well. Regards