guys seems like google do a few really good tools
http://sketchup.google.com/intl/en/
sketch 3d and 3d Warehouse.
This provides a really cool api to create some great mash ups with other bits of software (charlee:Macromedia Flash). You can also interface with google Earth hence local topography is done for you.
I know that this tread has moved away from archicad, but it will provide readers with alternatives.
I can also import my GDL objects library into these tools.
(bit more research needed, though)
Spiralvista
also the reverse is true see
http://www.graphisoft.com/products/archicad-solutions/sketchup.html