A new documentary called No Place on Earth describes the story of Ukrainian Jews who found refuge in caves after fleeing the Nazis during the Second World War.

When New York spelunker Chris Nicola went exploring caves in Ukraine in the early 1990s, he hoped he would find something incredible. But he never expected the story that expedition unearthed.

While exploring the gypsum cave system in the west of the country, Nicola discovered various household objects littering the ground, leading him to the realization that people had been living underground.

What Nicola didn't know at the time was the caves had been a refuge for Ukrainian Jews fleeing the Nazis during the Second World War, and that those refugees had lived underground for longer than anyone else in history.

The documentary tells the story of Nicola's discovery — and the stories of the men, women and children who lived in the caves to escape Nazi tyranny.

The documentary will begin its Canadian run in Montreal on Friday. The film will play in Toronto in June, and in the rest of the country later in the year.

CBC Radio's As It Happens speaks to the film's director, Janet Tobias, and then to two survivors from the caves, Sam Stermer and his niece, Sima Blitzer — both of whom now live in Canada.