That's maybe where I am lost.
I am on Drupal 7. I am sure that what I can do is simple, maybe some of you willl laugh with this.
Let's say I have 3 areas, 3 school areas. Each school area has 4 departments.
What I want is that all the content is classified under a "menu" (I am not sure now if I can call a menu) let's say a category. So when some content is created use created under one Area and One department. So let's say is content for Area 1 and Dept2, then the link menu would be:

- Area1
  + Department 2

And when I select to see content from Department 2, I should go to
-  Area1
   + Department 2

Menu, and I should see:

-  Area1
   + Department 2
      content 1
      content 2
      content "n"
      etc