Strange looking black artifacts

Hey
I started a new scene today and there are black artifacts on some objects (First Picture)
So I applied the subsurfe modifier, removed doubles and recalculated faces. Most of the artifacts dissapeared but there are still some left (second picture) which I can’t get away.
I hope you can help me with this problem.

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Since it looks like just simple extrusions, try deleting the top of the column, and redoing it. You definitely have some overlapping faces or inverted normals.