Window decorations made from paper doilies are something that many of you will certainly have seen or made before, but it is good to be reminded of it sometimes.
In a nutshell: Fold the paper symmetrically, cut a pattern into it, unfold it and voila!
If you would like more detailed instructions, you'll find them here.
Incidentally, paper doilies like these have a great deal to do with mathematics. The folds are the structural component that ensures that certain symmetrical patterns are created. The holes that are cut into the paper are the artistic component which is then repeated symmetrically. It is very much worth trying out different variations when you are folding the paper.