If you think Birdman was extreme filmmaking, wait until you see what Alejandro González Iñárritu has in store for his follow-up. Shooting this month in Calgary (average nighttime low: 9 degrees) the writer-director has partnered with Leonardo DiCaprio and Tom Hardy to tell the true story of Hugh Glass (DiCaprio), an American fur trapper and frontiersman in the early 1800s. After being mauled by a grizzly bear and left for dead, Glass made a heroic 200-mile trek back to civilization to find the men who abandoned him in his time of need, played by Hardy, Will Poulter, and Domnhall Gleeson.

Shooting with only natural light in remote locations left untouched by mankind, the arduous production extends until April since Iñárritu and his cinematographer, Oscar winner Emmanuel Lubezki (Gravity) can only shoot a few hours each day. “It’s a fun ride,” says the director, who has also reunited with his Birdman studio New Regency to make the film. (Twentieth Century Fox will release it on Christmas Day.) The Revenant continues Iñárritu’s interest in pushing the boundaries of filmmaking — an interest he developed initially on the technically-complicated Birdman–and one he furthers here as he delves into showcasing nature in as pure a state as possible. “It’s a very experimental thing that we’re doing here…I’m now addicted to doing things that can fail horribly or maybe that can give us a surprise. We are all into it.”