Suggestions about creating a big map

I have a project in mind that involves the design of my university as a 3D world (yeah, the whole place) and I have a poor knowledge about creating my own maps on Unity…

My question is, which is the best option to create a map like this?
Can I just use Unity3D primitives to put them together and get the shapes of what would be a building (for example walls would be cubes, floor planes, etc…) or is this a bad idea? How else can I do it? Google Sketch Up maybe?

It’s a simple project, not big deal, I’m not putting so much details on things.
Thanks.

I wouldn’t recommend Unity3D for actual modelling if it’s something else than just basic cubes/planes. A building is a bit more complex.

Since you’re not putting to much detail into it, I recommend creating the terrain in Unity3D, but the buildings with other software. You can usually just drag and drop the modelled buildings in your Unity scene.

Perhaps you can even download the buildings from Google Earth?

https://productforums.google.com/forum/#!topic/earth/Yli5tFi9F1Y