How to make an accessible city

So I've been into game development for a while and I've always wanted to build a little village or city. My only problem is that I'd want to build something with the potential detail from using say, Maya or Blender, but I'd want to be able to enter the buildings so that the village/city feels more alive. So my question is: How would I be able to make a building that you can enter and exit.

 

I don't really understand the question. By default you can enter any object. To stop you from entering a building, you'd have to arrange some colliders and use some a player controller that respects them.

Obviously you'll have to model the building interiors as well as exteriors. But assuming you've done that, what exactly is preventing you from entering them?

 

I'm not sure exactly what would be stopping them. I was mostly just wondering where I would want to build the building. Would I make the interior and exterior in Blender or would I just make it all in Unity using different pre-made assets?

 

Either way works fine. Do whatever seems easiest for you.