Summiting Mt. Everest is the pinnacle of any earnest climbers ambition. But it's fraught with all manner of hurdles, as the greater public will soon discover in Baltasar Kormakur's new flick Everest, which opened at the 72nd Venice Festival on Wednesday.

The mountain-climbing thriller is based on the catastrophic 1996 multi-expedition rush on Mt. Everest that left eight climbers dead, starring Jake Gyllenhaal, who plays Scott Fischer, one of two expedition leaders, and Jason Clarke as Rob Hall, the other.

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In real life, Fischer was the first American to summit the 27,940-foot Lhotse (just across from Everest) and Hall gained notoriety for raising sponsorship money to complete the "Seven Summits" in just seven months.

As with any movie based on true events, authenticity is key.

To re-create the climb, key cast members went to the mountain, climbing nearly to base camp.

"There's a tremendous responsibility trying to re-create something which has happened," Gyllenhaal said at the Everest Lido press conference.

According to Variety, Gyllenhaal and Josh Brolin spent time in a 30,000-foot simulator.

"We thought we could handle it, and we were feeling good. We were laughing and talking about the fact that we didn't think it was so bad, and then, all of a sudden, we got out of the chamber and just felt sick,” he said. “We realized the power of being so high up and what that does to your mind."

The film is set to release in the U.S. on Sept. 18.

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