Lights integrated into stairs. Late at night, the stairs can be lit (and safe) without ruining your night vision with bright overhead lights. Would also be a great way to really highlight a gorgeous staircase.
I want to do this for my kids to make reading exciting - for every stair, we'll read the book. Staircase to Knowledge by sungazing: Stairway to the reading room at The Magic House, St. Louis Children's Museum in Kirkwood, MO