London's bid to host the 2012 Olympics will be up against New York, Madrid, Moscow, Havana and Paris. BBC News Online reports on the climate in three of the Olympic favourites.
London's bid will renovate areas such as Hackney
Steve Schifferes in New York:
New York City is very confident it will win the race for the 2012 Olympics.
Hosting the Olympics is seen as a key sign of New York's revival following the nightmare of September 11, and New York easily defeated Washington DC and San Francisco in the earlier stage of the competition.
But New York's well-developed bid is very ambitious, costing $3.2bn and involving the redevelopment of long-derelict railway yards on the West Side of Manhattan into a new stadium, which would eventually host the New York Jets gridiron team or the New York Yankees baseball franchise.
Some local groups have opposed this stadium and the city funding guarantees may be threatened by the budget crisis.
But city and state leaders are working closely with the private sector and trade unions.
The plan also involves a major rejigging of transport lines to create a cross-town link from the Olympic Village on the East River in Queens to the stadium and to other venues in New Jersey.
The "Olympic X" plan is compact, placing 80% of venues within ten miles of each other.
The New York Olympic committee is planning to host world championships in wrestling, fencing and archery in the city this year to promote its bid.
The Big Apple offers superb cultural facilities, extensive mass transit links and a well-developed tourism infrastructure.
But concerns about congestion, crime and security could deter the Olympic committee.
Nikolai Gorshkov in Moscow
The head of Russia's Olympic Committee, Leonid Tyagachev, who happens to be President Putin's personal downhill skiing coach, told the BBC he was very optimistic about Moscow's bid to host the 2012 Olympics.
He said from a purely sportsman┐s point of view Moscow had all the necessary prerequisites - the infrastructure and experience of holding the 1980 Olympics and major international sporting events, like the Goodwill Games, and the CIS Youth Games.
The Mayor of Moscow, Yuri Luzhkov, has been treating these games, held for the past two years, as a springboard for the city's Olympic bid.
These days Moscow has no shortage of investors and is building 25 new sporting venues in and around the city without recourse to government funds, Mr Tyagachev said.
Mr Luzhkov said that during last year's International Olympic Committee (IOC) session in Moscow, committee members had a chance to see for themselves Moscow's level of preparedness.
IOC president Jaques Rogge has been quoted by Russian media as putting Moscow's chances as pretty high.
Moscow can count on support from Athens, in return for Russian support for the Greek capital's successful bid to hold the 2004 Olympics.
Sceptics point to the threat of terrorism, especially after the Chechen theatre siege in Moscow last October.
But Mr Tyagachev said the attacks of 9/11 in New York and Washington did not prevent the United States from successfully holding the 2002 Winter games at Salt Lake City.
He said the Beijing Games, slotted for 2008, could be at greater risk because of the Sars epidemic.
Emma Jane Kirby in Paris
Ken Livingstone has said the strongest competition will come from Paris and Madrid.
The strongest card in France's hand is that the infrastructure for an Olympics game is already here in Paris.
There is the Stade de France - a stadium built for the 1998 World Cup soccer championships with a seating capacity for 80,000.
It is in an excellent location - its very close to the airport - has good transport links to trains and buses and there is plenty of land around it which could be developed to house an Olympic village.
There is public support in France for the bid, especially as the country has been diplomatically frozen out by its anti-war stance, so a major sporting event like this would bring the spotlight back to France - they want the kudos.
But France also wants the money. The French economy is doing badly, there is rising unemployment, so an event like this would bring development and construction to Paris.
France has a good track record of hosting international sporting events - and was a close runner-up to Beijing for the 2008 Olympic games.
This time though it will not be satisfied with being runner-up, it wants the gold.