We've got this stump in our front yard. It's partially hollow, and always spends the spring and summer incredibly full of Black Widow spiders. Last year we tried building a little trellis on top and growing beans up it. It was nicer looking, but only made the spider problem worse.

I fixed it yesterday though! Just a couple of boards affixed into the gap in the side with copper coated hanger strap, and then a few bucketfuls of dirt.

Then I ringed the top in rocks, which I varied the size of to level off the top.