The biggest crowd I've ever been in was in Dublin in 1990, when the World Cup team returned home after getting to the semifinals. I believe that was the largest crowd in Irish history - the previous biggest was when JFK visited, and the football team was far bigger draw than the Pope had been a few years before. I can't find a figure on the web without paying, but I think there were about 2 million people on the streets of Dublin. (I was bang in the middle, outside the Bank of Ireland. Moving anywhere was not an option, you felt like a bubble in a head of Guinness).

There had been a practice event earlier in the day when Nelson Mandela had come to visit. The crowd hearing him speak was just as packed but it was a smaller street, the number was only in six figures.