The longtime sportscaster says he was kept in the dark for the surprise moment

bob costas
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For over 40 years, Bob Costas has been the voice behind some of sports' most unforgettable moments — but there's one memory he will cherish forever.

In this week's issue of PEOPLE, the longtime sportscaster, 69, recalls the emotional moment Muhammad Ali — who died in 2016 after suffering from Parkinson's disease for over 30 years — lit the cauldron during a surprise appearance at the 1996 Olympics in Atlanta, Georgia.

"It was a complete surprise for everyone in the stadium and everyone watching at home," Costas says of the historic moment. "And it was also a surprise to me and [fellow cohost] Dick Enberg."

Costas says that the head of NBC Sports, Dick Ebersol, purposely kept the two of them in the dark about the guest of honor.

"He told me and Dick Enberg a day or two before, 'I'm not going to tell you who it is. Almost nobody knows who it is. I want your response to be as spontaneous as people in the stadium and the people watching at home. You will know who he or she is the moment you see him or her, but I'm not telling you who it is.' "

muhammad ali
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"It was only when Janet Evans reached the top, that Mohammad stepped literally out of the shadows to accept the torch from her," he continues. "And even then 20 years before his death, you could see the effects of his Parkinson's disease. He was trembling and his ability to speak had been compromised already."

Recalling the 'profound' moment, Costas, whose new HBO show Back on the Record premieres Friday, says the three-time world heavyweight boxing champion's presence created an uproar unlike anything he's ever experienced.

"You hear a lot of sounds in an arena or a stadium, but one I'd never heard before since, was an audible gasp," says Costas. "Then, that was replaced by thunderous and sustained applause. And not only was it an exciting moment, it was also a poignant moment because of the arc of his life."

"But it was also, ultimately, a moment of reconciliation because as popular and powerful as he had been to much of America, he was also unpopular at one time to much of America," he says of the legendary Ali. "He was a polarizing figure, but in that moment you could feel, that it had all come back together. Even those who might not of agreed with some of his stances, had to in the long run, respect and admire him for having the integrity and the courage of his convictions. And now they had to admire him for being willing to fight through cruel reality of what the sport that made him perhaps at one time the most famous in man world, the price he ultimately paid for that."

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For Costas, who has hosted a dozen Olympic Games over his career, the moment hit differently than any other.

"It was such a combination of emotions, all of those various elements of recognition, all those elements of who he was came together at that time he says. "And he said himself afterwards, he felt as if it was a born again moment."

"Ali was a beautiful figure in a brutal sport," he concludes. "Someone who was the epitome of grace and so entertaining and quick witted, but still able to move a stadium full of people, with thunderous cheers and maybe even some tears."