WATCH: Shailene Woodley & Theo James Tackle ‘The Wall’ in ‘Allegiant’

ET had the ultimate fangirl experience by going behind the scenes of one of next year’s most highly anticipated movies, The Divergent Series: Allegiant.

Shailene Woodley and Theo James discuss with ET on what it was like filming one of the movie’s most intense stunts – tackling “The Wall.”

In the sci-fi adventure flick, Beatrice Prior (Woodley) and Tobias Eaton (James) get past the wall enclosing Chicago and venture into the world outside, which they quickly learn is more dangerous than ever before. The duo must determine who they can trust as a ruthless battle erupts in their new environment, which threatens all humanity.

“We did this bit when Shai had to be facing down and I had to be the other way, and it was a little daunting,” James said of scaling the 60-foot concrete structure.

“I was facing the ground, walking backwards,” Woodley explained. “I was holding onto Theo’s shoulder like it was the last thing!”

The Divergent Series: Allegiant hits theaters March 18, 2016.