Importing DWG Into SketchUp Pro

[Wogan]

Greetings,

I am having some trouble in importing a DWG into SketchUp, the CAD file is quite large (15MB) as it covers most of an entire city (17 kilometers x 17 kilometers of the city). After it imports, there are many missing lines, and due to size and complexity, to redraw them in SketchUp would take hours if not a couple of days. Aside from saving as an older version of CAD, is there anything to prevent lines not being imported or disappearing all-together? This is for an Architecture studio class, concerning Urban theories, hence the enormous dimensions.

Any help is greatly appreciated.