Permanence & Wayfinding

This is something that we don't do that much anymore in our built environment, that is to make a permanent mark for something that may only have temporary value.  Here we have a north arrow set into the concrete sidewalk in downtown Boston.  Why would someone do this?  It is not a part of a larger mural or other work of art, it is simply an arrow and the letter "N".  But somehow the person funding the building project decided to spend some extra money to have this laid into the sidewalk and probably had no return on the investment.  That must've been a hell of a sell by the architect if it was in fact the architects idea.  I have clients that would never spend money on anything so seemingly frivolous.  But then, we all value things differently don't we?  I would spend the extra money to lay this in the sidewalk, yet the Freedom Trail Foundation has laid out their red line here in paint rather than the brick that they have done in other parts of it.