Colliders do not seem to be working

I want my user to navigate through an urban landscape with lots of buildings, but even with colliders on all of the buildings, the first person controller can walk straight through. Any suggestions?

Without any more detailed information about your scene it's difficult to say, but there are a few things which can result in colliders not colliding with each other:

  • If either object is marked as 'trigger', it will not physically collide with other objects
  • Mesh colliders cannot collide with each other unless they are both convex, or unless one is static and the other convex.
  • If a collider starts off in a position which is penetrating another object, collisions won't work between them until they become separated.

There's a table called "Collision Action Matrix" at the bottom of this page which (although badly presented!) might help provide more information:

http://unity3d.com/support/documentation/Components/class-BoxCollider.html

i fix it … i use a mesh collider and set CONVEX insted a box collider
hope this help