CHICAGO (CBS) — Trailers and generators line the Dearborn Street Bridge as crews prepare for Nik Wallenda’s tightrope walk on Sunday night.

“It’s a major operation, we have 100-200 people working on this. We’ve been here since Friday and we’ll be here for another week and a half,” said Marc Weinstock, director of technical operations for NBC Peacock Productions.

Weinstock also handled the preparation and broadcast of Wallenda’s Grand Canyon tightrope walk.

“The last show we did was at the Grand Canyon and it has it’s own challenges because it was the middle of nowhere but the benefit was that it was the middle of nowhere and no one cared but being in the middle of Chicago, everyone cares,” he said.

Weinstock said safety is key, because anything can happen as Wallenda’s high-wire walk is broadcast live to 220 countries.

“It’s very very nerve-wracking. There is no trick, or no gimmick to what Nik does. It’s the real deal. It’s really a guy standing out there in the middle of the city on a rope, 700 feet above the ground and it’s very intense whether you are part of the show or not,” he said.

Wallenda will walk from Marina City’s West Tower to the Leo Burnett building, 50 stories above the Chicago River. He’ll then turn around and walk a tightrope between the two towers blindfolded.

Not only will this be the highest skyscraper walk in the history of the Flying Wallenda family, it will be the first time that he has ever attempted it at such a steep angle. Dozens of cameras will be positioned across the city to capture the event that begins at 6 p.m. Chicago time on Sunday.