This silent movie from 1925 was produced and directed by Ernest Schoedsack and Merian C Cooper, who went on to create King Kong.

Grass is a real-life adventure travelogue, in the manner of Nanook of the North, showing the kind of derring-do which goes far beyond our tame concept of the "documentary".

It depicts the migration of the Bakhtiari tribe on a two-month-long journey across Iran in search of pasture for their flocks, with extraordinary, epic shots of the 50,000 tribesmen and their beasts snaking across the vast landscape.

If DW Griffith, Ernest Rutherford and Rudyard Kipling could collaborate on a movie, it might look like this.