Check out kinto.sh, which does this for you:
The Windows key is a tragic misstep in computer evolution. It should not exist.
The "Windows key" is just Microsoft branding. It was called the Super key before that, and it dates back to the 1970s.
Here's an example on a Sun keyboard, labelled with a diamond: http://xahlee.info/kbd/iold51593/Sun_Microsystems_Type_6_Key...
I mostly SSH to Linux, but when I use a Linux Desktop, I struggle to get the key bindings to my taste.