This is a genuine example of wrong mental model mapping. When I look at the sign, I’d expect the A floor to be the TOP floor. Quite opposite. A floor is at the bottom of the building and C floor at the TOP. Passing this sing I always have a strange feeling climbing the stairs to get to the C floor :). It should be two stories beneath the ground.
EDIT 31. 1. 2012: Here is the actual photo of the building with marked levels (thx lil)