In social experiment backed by Volkswagon, stairs to a subway entrance in Stockholm, Sweden were retrofitted to play the notes of a piano with each step taken.
According to the video (above) the musical stairwell led to 66% more people than normal to climb the stairs instead of coasting up the escalator.
Naturally, the piano stairs inspired fond memories from the iconic scene in "Big" when Tom Hanks' character rocks the oversized piano in NYC's FAO Schwarz (below).