Need help with selecting nurbs in city - big scale

Hello, I have been building a Lego City on Maya, using polygons for the bloks and nurbs cylinders for the dots on top. I built it block by block and duplicated etc. My problem is, that all the nurbs cylinders are really slowing down my computer and making it really slow to render a single frame.

Because I have nurbs cylinders on each block, and there are multiple blocks stacked on each other, I think that by deleting the cylinders that are not visible (between blocks), Maya will run much faster and render times will also improve.

The thing is, I need a quick technique to select all the nurbs cylinders that I don't need (all the ones under the top layer of blocks). All my buildings are different sizes so i can't just enter a side/front view and marque select all the cylinders I don't want.

I've had two ideas so far, both failed. The first was to use the paint selection tool and in the top view, just paint all the nurbs cylinders I want and delete the rest, but it turns out you can't use the tool to select objects, just components.

The other idea was to turn on ignore backfacing, but again, it only works for polygonal components.

Please give me some advice. It will take forever to manually select them as I have around 30,000 blocks of lego with 4 cylinders in each.

Thank you in advance.