PBS presents a preview of the new Ken Burns film THE NATIONAL PARKS: AMERICA'S BEST IDEA. The 12-hour, six-part documentary series, directed by Burns and co-produced with his longtime colleague, Dayton Duncan, who also wrote the script, is the story of an idea as uniquely American as the Declaration of Independence and just as radical: that the most special places in the nation should be preserved, not for royalty or the rich, but for everyone.