Levitate Architects used a staircase to a loft-like bedroom to create an enormous amount of book storage space. Even though the staircase isn’t very compact but could accomodate so many books that it would save some space anyway.
Do you have some wasted space in a staircase? Here’s an idea for that expanse of air: put a hammock in it! OODA Architects did that in a house and now there’s a “lofted” space by a window for reading, sunning and relaxing. Fun and yet.
"A tubular steel slide plummets through four storeys inside this penthouse apartment in New York by architect David Hotson." I like the slide idea, but I imagine going up would be much harder than coming down. unless you use the stairs, of course!