The delegations of the three remaining candidates for the 2020 Olympics arrive in Argentina to make their final pitch. Within hours, the host city of the 32nd summer games will be announced.
Istanbul. Madrid and Tokyo have the task of winning over the 100 International Olympic Committee (IOC) members with their presentations on Saturday afternoon before the voting begins.
The identity of the winning bid will be announced at 21:00 BST on Saturday.
Tokyo is the favourite to win the games, followed by Madrid, with Istanbul the outsider, but as previous bidding processes have proved, this can count for little.
In 2005, Paris was the bookmakers' favourite, the day before the vote, followed by London and Madrid with New York and Moscow outsiders.
On the day, Madrid was leading after round two, by which time Moscow and New York had been eliminated.
But the Spanish capital was knocked out in the following round, leaving London and Paris to fight it out for the votes going spare after the other three cities' elimination.
Speaking before the vote, the then sports minister Richard Caborn had commented how history shows with the Olympics that the favourites "don't always come in".
"There's been more occasions when second favourites have come in... It will be a handful of votes that determine it."
That bodes well for Madrid, who like London in 2005 has seen its odds shorten in the final 24 hours.
In 2005, when Russian and US leaders Vladimir Putin and George W. Bush stayed away, their countries were eliminated in the first round. That left Britain and France, with both their leaders in attendance, to try and out-do each other on the schmoozing.
This time round, all three leaders are expected to lead their countries' delegations to the IOC.
Tokyo, Japan: favourite
Of the three candidate cities, Tokyo is the only one to have hosted the Olympics, back in 1964.
There is no question about Japan's big tournament pedigree, in recent years it has hosted the football World Cup and the Athletics World Championships.
But since those events, Japan has been rocked by a tsunami and the Fukushima nuclear disaster. Recently, news broke that 300 tonnes of highly radioactive water may be flowing into the sea every day.
Despite this setback, the Japanese has assembled a well-prepared delegation who are aiming to reassure delegates jitters over the Fukushima fall-out.
Tokyo is seen as the safest option with fewer risks - it is a modern city with good public transport, compact venues and short travel times. Some argue that the sentimental factor of using Olympics to help Japan recover from 2011 earthquake and tsunami might actually work in its favour.
Madrid, Spain: second favourite
Spain hosted the highly successful Barcelona Olympics, which raised the profile of country's long-neglected second city and the wider Catalonia region.
But hopes that it could repeat this success by hosting the 2012 or 2016 were dashed when it missed out in the IOC votes.
Spanish Prime Minister Mariano Rajoy, who was present as leader of the opposition for Madrid's last two IOC defeats, believes that Spain is in a great position to win the 2020 games.
"This is the third bid in a row but this time 80 percent of the installations are built," he said.
Spain's economic struggles, highlighted by a 27 percent unemployment rate, are regarded as the main weakness of Madrid's bid. But Madrid regards its streamlined proposal as a strength and claims it has one of the lowest Olympic budgets ever.
"The investment required is much less than the other bids as we have already presented two so almost every one of the stadia are ready, the football, the swimming and the track and field to name a few," said Rajoy.
Istanbul, Turkey: outsider
A youthful delegation has been sent to Argentina to reiterate the young population of the country, perhaps with a nod to the successful London 2012 campaign which emphasised youth.
Like Madrid, Istanbul has been at this stage before with two failed bids since the turn of the Millennia.
As before, it is emphasising its unique selling points as a bridge between continents and cultures and also the prospect of becoming the first Muslim country to host a games.
But as with previous IOC meetings, the city's lack of infrastructure is tipped to hold it back in the vote. And the sight of riot police in Taksim Square earlier this year may have also harmed its chances.
20 June 2011