EXCLUSIVE: If you’re afraid of heights, you might want to brace yourself for the new trailer for the National Geographic documentary Free Solo, which was just tipped for a slot at the Toronto Film Festival next month. The pic depicts climber Alex Honnold’s attempt to scale the world’s most famous vertical rock face: Yosemite’s 3,200-foot  El Capitan peak…and he does it as a free solo climb without a rope or net. It’s quite a feat that an average person will see as wildly insane, but for Honnold, it’s an exercise in unlocking one’s human physical and mental potential.

The documentary is directed by world-renowned photographer Jimmy Chin and award-winning documentary filmmaker Chai Vasarhelyi. The two aren’t strangers to the world of climbing, having collaborated on Meru, which is lauded as one of the best of its genre.

As seen in the trailer, the filmmaking puts the awe in awesome with death-defying angles and picturesque shots of Honnold making his ascent last summer. The film is grounded as they show how his ambition affects his relationships, but the spotlight shines on Honnold’s incredible climb. which will make anyone’s heart stop. (SPOILER ALERT: He makes it to the top. But it’s let’s face it — it’s his jaw-dropping dramatic journey that makes it worth the experience.)

Free Solo is set to open in theaters September 28.

Check out the trailer above.