In June 1977, visitors to the Gallery of Modern Art in Bologna, Italy, were met with a shocking sight: Marina Abramovic, the Serbian performance artist, and her partner, Ulay, standing in the museum’s doorway, completely naked.

The only way inside was to squeeze between the couple.

Abramovic and Ulay remained in place for three hours, staring intently into each other’s eyes, as a stream of visitors pushed through and sometimes stepped on their toes. Then, the police arrived, and shut down the performance as obscene.

This fall, Abramovic, now 76, is restaging that work, “Imponderabilia,” at the Royal Academy of Arts, in London, as part of a major retrospective of her work that runs through Jan. 1, 2024. Since Abramovic no longer performs the work herself, and Ulay died in 2020, she has recruited younger performers to take part — and there is another major difference from the 1977 piece.

If a visitor would rather not squeeze past a naked man and woman in a three-foot-wide doorway, they can walk through another entryway to the left, and skip the experience entirely.

In an age when museums are grappling with how to show audiences challenging work, and adopting measures to protect artists and staff, Abramovic is also adapting her old works to suit contemporary mores.

On a recent morning, most visitors chose that nonconfrontational route, until Sarah Raper, 59, gave her coat to her husband and announced: “I’m going to do it!” Raper then briskly pushed past the naked man and woman, facing the female performer.

“That was quite unsettling,” Raper said afterward; it felt like “a real invasion of personal space.”

Jason Speechly, 60, stood watching the two naked performers curiously for several minutes but then opted for the other door. “I just got sheepish and followed the rest of the crowd,” he said.

In an interview, Abramovic said she’d had “millions of meetings” with the Royal Academy’s staff to ensure “Imponderabilia” and three other provocative performances could be included in the retrospective — and she was now conflicted about the compromises that she had made.

If “all of these restrictions we are facing now” had been in place in the 1970s, she said, 80 percent of her works would never have been performed. On the other hand, Abramovic said, artists should not “live in a prison of your own promises” and refuse to change with the times. By making concessions, a new generation was witnessing her art, she said. If she’d complained about the new doorway for “Imponderabilia,” the performance would only exist as “a stupid gray photo in a book” that no one would ever see.

“Really, the smart thing to do is compromise,” she said.

Abramovic has done this with “Imponderabilia” before: In 2010, for “The Artist is Present,” a career survey at the Museum of Modern Art in New York, Abramovic said that MoMA asked for the performers to stand far enough apart so that a wheelchair user could pass between them. “I felt the piece really suffered for that,” she said.

MoMA’s lawyers also asked for significant changes to “Luminosity,” a 1997 endurance feat in which Abramovic sat naked on a bicycle seat mounted high on a gallery wall for six hours while holding her arms and legs outstretched. The MoMA presentation used other performers, and the day before the opening, Abramovic said, the museum’s lawyers insisted that they needed to wear a helmet and safety belt.

“I said, ‘This is ridiculous!’” Abramovic recalled. “‘It’ll become a ridiculous work.’” She said she ended up signing documents that made her personally liable for $1 million in case of any accidents, and the piece went ahead as planned.

MoMA did not respond to a request for comment. Klaus Biesenbach, a former MoMA chief curator at large, who organized the 2010 show, said in an email that he couldn’t remember “details and anecdotes” as well as Abramovic can, but added that “it was a miracle” that the exhibition took place.

Biesenbach is now the director of the Neue Nationalgalerie in Berlin, where he recently saw another example of how attitudes to performance art have changed over time, he said. Earlier this month, the museum restaged Yoko Ono’s “Cut Piece,” a 1964 work in which audience members are invited to snip away a performer’s clothes with scissors. The audience behavior today was very different from the 1960s, he said, with visitors aware that there was a “‘right’ or correct” way to act, and conscious that hundreds of cellphone cameras were trained upon them.

Andrea Tarsia, the Royal Academy’s director of exhibitions, said that most of the changes for the Abramovic show were small and made for the performers’ safety and comfort. With “Imponderabilia,” for instance, the doorway was heated so that the naked man and woman, who stand there for up to an hour at a time, don’t catch a chill.

Nearby security guards also keep an eye on visitor behavior, Tarsia said, and at the end of each day, the performers gather for a “detox” session to discuss any uncomfortable moments that occurred. All performers would have access to therapists, Tarsia added.

And even if visitors avoid squeezing past the naked bodies, Tarsia said, the work would get them thinking. “In art, when something riles you, that’s often where the interesting bit is,” Tarsia said. “Maybe if people choose not to go through the door, they’ll later reflect on why they made that choice,” he added.

Abramovic, who recently survived a life-threatening embolism and spent time in a coma, said that she did not mind if only a handful of visitors experienced “Imponderabilia” as she originally intended it. Artists, she said, committed to their performances no matter what happened during them.

“If there’s an earthquake, if electricity stops, if somebody walks into you, it’s all part of the work,” she said. “And if nobody passes, that’s still part of the work.”