Perhaps not the “best” but certainly in my top 3 and a bit different than what everyone else shared. If you like art you need to watch it. You can get it free on Kanopy if you have a library card.
Vimeo
Watch Troublemakers: The Story of Land Art Online | Vimeo On Demand
A film by James Crump "Takes its place among the great art documentaries of the last half-century." Eric Gibson, The Wall Street Journal Troublem...