While not particularly decorative, this is visually interesting. It’s a rope trick (and it’s definitely a trick, watch her hands carefully. Here’s the video:
http://www.math.toronto.edu/~drorbn/Gallery/KnottedObjects/WaistbandTrick/index.html

Here’s a line diagram of what’s happening from Kauffman’s On Knots (page 98-99) via Google Books
http://books.google.co.jp/books?id=BLvGkIY8YzwC&pg=PA98

The family spent many minutes trying to figure out where the switch happened (because you have to let go of the end at some point in order to actually create a non-unknot, it’s towards the end while the other hand is doing kind of unnecessary gestures).

Actually, if you go to the knotted objects page (http://www.math.toronto.edu/~drorbn/Gallery/KnottedObjects/) you’ll see more knot tricks and some very cool sculptures and objets d’art.