The enormity of the crowd was matched by the momentousness of the occasion. People were struggling to breathe and to see, getting tetchy with each other, and it felt "kind of unsafe". A woman went into labour and the crowd just parted - "she came stumbling through, holding her stomach".
"There was one black man whose daughter and husband had taken him. He just had tears in his eyes. He never thought he would see anything like it."
Anna McDonald, a 17-year-old pupil from St Paul's Academy in Dundee, was standing in the midst of it all, looking across to where Barack Obama was being sworn in as the 44th president of the United States of America. Beside her was classmate Lewis Smith.
They were attending Obama's inauguration on a five-day visit to the States at the invitation of the Congressional Youth Leadership Council. They had, on a previous occasion, participated in the Global Young Leaders Conference in Washington DC and New York, a demanding programme which included a simulated general assembly at the United Nations.
The "most outspoken ones" were invited back, says Lewis. So he and Anna won their places, unbeknownst to each other, before their schools merged (Anna was at Lawside Academy, Lewis at St Saviour's). They paid pound;2,500 each to join a hectic schedule last month, which also took in speeches from anti-apartheid activist Archbishop Desmond Tutu, former US vice- president and environmentalist Al Gore and Colin Powell, former US Secretary of State.
Anna recalls inauguration day most vividly through "the people I saw and the attitude they had to each other" while the main action took place a few hundred yards away. Lewis was struck by the sense of unity behind Obama, straddling ethnic groups and even staunch supporters of his presidential rival, John McCain: "I never heard a negative comment about Obama." He hoped to catch exactly what each speaker said, but "a lot of the people were so hyped up it was difficult to hear".
The new president's speech was the high point for Lewis, a keen student of American history, reminding him of Thomas Jefferson and making clear that he would ditch isolationism and appeal to common values. "I felt I'd have been proud to be American at that time," he says.
It was "so easy to get swept up" in the surge of optimism, says Anna, who believes there were two types of Obama supporters: those who voted on policy, and those carried along by the feelgood factor.
Lewis, while an admirer of Obama, could not understand his huge popularity even among peers with little interest in politics or knowledge of Democrat and Republican ideals: "In our old common room, there were posters of him on the wall."
But being in America helped him appreciate that Obama had "a certain charisma" which struck a chord.
"When he talks, people just listen," says Anna, who wears a prefect badge on her left lapel and a "Yes you can" badge on the right.
The mix of measured delivery and progressive policy also had mass appeal: "He's a calm radical," says Lewis. Yet "he's still got that conservative side to him", which means he does not rule out sending troops into Pakistan and does not back gay marriage, the latter "a bad reflection on Obama's character" but the type of stance Lewis concedes probably resulted in the support of less liberal voters.
Both pupils were disappointed with British media reports. "I don't think the BBC captured the mood or excitement," says Anna, while Lewis was surprised on his return home about the fuss over Obama's verbal stumble. "I didn't really notice it at the time," he says. For him, such trifles distracted from the significance of Obama's election. "I think it's a bigger deal in Americans' eyes than we can understand," he says, believing the UK equivalent would be to elect a Muslim of Pakistani origin.
Lewis and Anna are irked by the stereotype of the fat, stupid American. Despite all the faults they see in America, they have been inspired by the country's sense of possibility which Obama has reinvigorated with his historic election.
Americans "don't care where you are from", says Lewis, while people in the UK can feel superior about certain things: its welfare state trumps America's iniquitous healthcare system but it is more socially stratified. At home, he admits to having felt ill at ease in the company of private school pupils; across the pond, he was struck that a renowned millionaire thought nothing of stopping to chat to him.
The American experience has ensured that, where once Anna worried about having a clearly defined career path, now she just plans to head for St Andrews University to study international relations and remains open to the range of possibilities thereafter.
The crowd at the inauguration amounted to nearly two million; Dundee's population is 142,000: "Coming from a smallish country and a smallish city, you don't appreciate that there's a whole world out there."