People gathered from early morning hoping to gain the best vantage point from behind the metal railings along the route in the city centre.
By the time Charles and Camilla passed by in the royal cavalcade along Wellington Place, Donegall Square North, Chichester Street and Victoria Street to loud cheers and applause the crowd was 10 deep in some parts.
People described the atmosphere as “emotional”, “happy” and “full of excitement”.
Many people held their phones above the crowd to capture a recording of the historic moment.
Charles and Camilla attended a number of engagements in the region on Tuesday as part of the King’s tour around the UK’s home countries.
The King and Queen Consort arrived in Belfast airport shortly before making their way to Hillsborough Castle, the royal residence in Northern Ireland where the royal couple met Northern Ireland political leaders, and received a message of condolence.
They also viewed an exhibition of pictures showing the Queen in Northern Ireland.
After attending a memorial service for the Queen at St Anne’s Cathedral, Charles and Camilla then undertook a walkabout at Writers’ Square, before leaving Northern Ireland.
Nine-year-old Abby Preston, who was waving a flag alongside her little brother Adam and her Mum and Aunt, told the PA News agency she was “really excited”.
They had queued from 9am and waited for hours to see the King and Queen Consort drive at about 2:45pm.
Her mother Jennifer said her daughter was “more excited” about it than her 10th birthday this week.
Robert Parks, 64, from Portadown, occupied a prime spot along the railings with a Union flag with a printed picture of the Queen.
He said he was taking part in an “act of history”.
“It won’t happen again in my lifetime,” he added.
Mr Parks also gave his sympathies to the King.
“The shock of his mother dying was a shock to us all,” he said.
“Good luck to him, I wish him all the best.”
Diana Gott and her friend Helen Elliott travelled from Enniskillen to join the queue outside City Hall.
Ms Gott said it was a “privilege” to be there to see the King, adding there was a great atmosphere, and that everyone was “happy“ in the crowd.
Ms Gott, who will travel to London for the Queen’s funeral on Monday, said she had met the Queen 10 years ago when the monarch visited Enniskillen.
“I loved the Queen, she said. “She was a remarkable woman and a great example to the nation.
“My granddaughter gave her flowers and I was holding her and I met her and that Duke of Edinburgh, she was lovely and so was he. He was quite jovial.”
Her friend Helen said it was an “emotional” as she described how she has a framed photo hanging on her wall at home of Charles shaking her hand.
Rebecca Hanna, 22, from Killeen, Co Down said: “I just wanted to see him pass and watch the service.
“I’m just surprised by how happy it is. Just because it’s Belfast, you’re not sure what it will be like – it might be a bit tense – but not, at all, it’s been really good.”
Andrew Hutton, from Conlig, Newtonards, said he had come to the city to pay his respects to the King.
Mr Hutton described the Queen “as a one off”. She was an ambassador for the whole world, not just Northern Ireland and the UK, he added.
Carla Cabal, from Mexico City who was in Belfast on holidays, said it was a “wonderful opportunity” to see the King.
“It was great emotion to be here,” she said. “It was exciting. I never thought I’d be part of this moment of history.”
After the King and the Queen Consort passed members of the public gathered at City Hall to watch the church service for the Queen at St Anne’s Cathedral being televised on big screens.
Katie Gaston brought her two young daughters Miriam, eight, and Esme, six, into the city for the day.
Miriam told PA it was “exciting” to see the King.
“We saw his head and his face and a bit of his hand,” she said, adding that they gave him a wave.
Their mother said: “We thought it was important to bring the girls in.
“I’ve never seen anything like this so obviously they haven’t either. It’s a moment of history.”
Mrs Gaston said the Queen had “always been there”.
“This is a moment that I think it’s really important that we mark, she said.
“I say thank you to God for her life, for what she did for us and the example that she was, especially her faith, that she was steadfast and tried to stay true to what she believed in.
“That’s something that we try to bring up in the girls.”