Here’s where this was shot. As far as I can tell, this is for real, though the people probably look closer to the hot stuff than they actually are because telephoto lenses compress distances.
The New Zealand mountains Ruapehu and Ngauruhoe were Peter Jackson’s stand-ins for Mt. Doom, but the video above is closer to my mental image of Tolkien’s volcano. (Tolkien is said to have modeled Mordor on the perpetually erupting Stromboli.)