Modeling - symmetrizing part of a mesh I am currently working on the column.  When I smooth shaded it to see how smooth it is I noticed that the ring base of the column is not perfectly smooth because the to sphere modifier I used to make the square base round mess this part of the mesh a bit.

 



Is there a fast way to make blende smooth or symmetrize the part of the mesh highlighted in the photo?  

I tried to do it but retouching single vertices but it will never be perfectly smooth.

Thanks in advance for any help.
You can correct this shape manually, using two tools.

01) Scale tool
- correct the height of edge rings, so they're level.
- just scale them to 0 along the Z axis  



02) To Sphere Tool
- this tool will make a circle from any shape
- you can use it to correct the roundness of your edge rings
- select the edge ring and go Mesh > To Sphere (click anywhere to activate it)