Hi everyone, I have a big shapefile where some polygons are falling completely within others as shown below. These polygons are on the same layer.

I want to be able to:
- Find all features that are within other features
- Delete/Merge the internal polygon into the outer polygon
I imagine this is possible, but I can't get it to work. I have tried to use the Select By Location and the within/completely within relationships to select them all but have had no luck, the tool simply doesn't select them