Zooming in/out normally works fine, but I wanted to see the 3D view from further out, so I tried adjusting the "cloth map zoom level" to around 40%.  This worked great until I noticed that my city improvements were no longer visible:

The smoke and sparkle effects were still going, the fence was there, and I could mouse over the spots and it would say what was there, but the actual buildings were gone.  Zooming in/out does not fix the problem. 

I then quit the game, reloaded the save and tried again, setting the zoom to about 30%.  I zoomed out, and upon zooming in, the buildings were gone again.

Video card: Nvidia GTX280.  I'm running 1600x1200 with most display setttings maxed.

OS: Windows 7 64-bit

I can provide a screenshot and/or further details if you need them.