When a sign and a mental model don’t match – a poor interaction

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)