Fabulous solution when space is too tight for a standard hinged door. You can also put furniture on the walls next to this opening, just leaving enough space behind the furniture for the doors to slide.
Acid-stained Concrete Patio -- Looks like copper! Click the pic for a brief how-to video on doing this technique. I'd love to do this, although I wonder if the acid stain is bad for those plants around the patio.