In a large industrial building on the outskirts of Montreal, 14 Russian trapeze artists and six aerialists gathered for rehearsal in a studio the size of an airplane hangar. They were in the final months of choreographing "Zarkana," Debra Brown's 11th creation for the circus company Cirque du Soleil. The show cost $50 million and opens in June at Radio City Music Hall.

"I can't wait to see this," Ms. Brown said as three young acrobats climbed into metal rings suspended from the 75-foot-high ceiling....