I created a polygon which covers a park. But I want to distinguish some small buildings located inside the park. Consequently, I want to distinguish them and use them as independent patches inside the original polygon. I used do it the "Add ring" function in the QGIS 2.2. But I don't know, how can fill those empty holes, which were resulted. I tried the "Fill rings" options (in QGIS 2.2), but I was not lucky with it.
Does anybody have an idea, how can I fix this problem?