Those pillars are floating 1 or 2 units off the ground. I would make them touch the ground (or even intersect with the ground).
If you are using current tools then you can make the pillars into a brush entity func_detail_wall, or func_detail, give them "_shadow" "1" as keys/values (I would also give them "_phong" "1" for a smoother shading).
You can also add dirt mapping for baked ambient occlusion - run:
light.exe -extra -dirt
The tools I would use are here: