It was as much a grandiose act of aerial ballet as a feat of engineering. In the dark chill of an October night, a towering red crane hoisted a massive burnt-orange span on a thick metal cable. Workers clad in yellow safety vests guided it with long ropes through a slow pirouette. Then, the crane eased it down as gently as 242,000 pounds of steel can be lowered.

And with that, the largest piece of the Northeastern University Pedestrian Crossing was in place. At 132 feet long, the piece spanned the five MBTA and Amtrak rail lines that divide the Boston campus, forming a physical link between the two sides.

The dramatic construction of a visually stunning bridge that promises to become a landmark for the university is a key component of Northeastern’s vision to join the Boston neighborhoods of Roxbury and Fenway, and reimagine Columbus Avenue. The placement of the bridge follows the reopening in August of the Carter Playground as a state-of-the-art recreational park, refurbished and maintained by the university, and the development of International Village and the Interdisciplinary Science and Engineering Complex.

“We are unique, in that we have a railroad that runs through our campus,” said Kathy Spiegelman, Northeastern’s vice president and chief of campus planning and development. “And for a long time, that railroad was a barrier.”

But recent efforts, including Northeastern President Joseph E. Aoun moving his office to the southern side of the tracks, have “begun to make it clear that Columbus Avenue was another front door for the campus,” she said.

Spiegelman was speaking to a crowd that had gathered in the auditorium of Northeastern’s Interdisciplinary Science and Engineering complex for a midnight master class, where representatives from each of the firms involved, Payette, Arup, and Skanska, laid out what it took to make this bridge a reality.

Fueled by midnight pizza, cookies, and copious quaffs of coffee, the audience included students, as well as professors representing the schools of engineering, architecture, and business, and professional architects, engineers, and designers.

“In class they learn about a lot of construction,” said Hao Sun, an assistant professor of civil and environmental engineering whose students attended the class. “But it’s really a great opportunity for them to see construction at night on campus. And this is a really unique bridge.”

Putting the span into place was a three-hour job. Such a heavy piece required one of the largest cranes on the East Coast to lift it, and the job had to be done slowly and carefully. Also, one of the speakers at the master class pointed out, the bridge was facing backwards and needed to be lifted, spun 180 degrees, and then moved over the train tracks. And this process couldn’t begin until the last train had run through, and the MBTA and Amtrak had turned off power to the railway.

The construction crew had been gearing up for this weekend (a smaller piece was lifted into place early Saturday morning) for weeks. The bridge had been shipped in pieces from a fabricator in Houston, Texas, and the massive crane had to be shipped from Maine and then assembled on-site.

“We spent a week building this crane and we’ll spend a week taking it down again, all for these two nights,” said Jessica Acosta, the quality engineer for Skanska, the construction firm.

This process began six years ago, with the overarching goal of welcoming and encouraging people to cross.

“The vision for the bridge was born out of this idea of flow and movement,” said Bob Shaeffner, who is a principal at Payette, the architecture firm that designed the bridge. “Play down the tracks as an impediment and make an event. Make the crossing almost an artistic experience.”

There are no right angles on the bridge, which will open for traffic in 2019. As it curves asymmetrically across the tracks, steel walls, turned rust-red over time, will flare up and out on either side. The southern wall will be solid, with a string of LEDs lighting the way, while the walls of the northern side will fan out like gills, revealing views of the Boston skyline and the Interdisciplinary Science and Engineering building.

Shubham Goski, one of the students who attended the event to understand the design and construction of Northeastern’s newest addition, said that when he first heard about the bridge, he didn’t immediately grasp the significance of the project.

“In my mind, it was just a pedestrian bridge,” said Goski, who is pursuing a master’s degree in civil engineering at Northeastern. “How important could it be?”

But when he saw some of the design plans, he knew he had to show up to watch it be put into place.

“We never get to see infrastructure construction live,” he said. “If you get an opportunity to go, you go.”

Gabriel Cutrone, a second-year student in civil engineering, stayed until almost 3 A.M. discussing the project with Acosta.

“This was a great opportunity to see everything that we might learn in class put into actual practice,” Cutrone said. “And something really specific to Northeastern. It’s kind of historic.”

Ian Thomsen contributed to this report.