There is now just a week to go until each city bidding for the 2012 Olympics must hand over its final dossier to the International Olympic Committee.
The IOC's evaluation of the five bids in May left each venue with plenty of fine-tuning to do in order to distinguish itself from its rivals.
So what are the key weaknesses that the cities have been trying to address?
GOVERNMENT AND PUBLIC SUPPORT
Madrid scored the highest number of points in the IOC evaluation, with Paris just behind.
London was criticised by the IOC after an IOC poll revealed that public opposition to the bid was higher than in any of the other cities.
London's bid had produced a poll saying 82% of Londoners were in favour - but the IOC poll had that figure at 67%.
"It is vital that we engage with the British public," admitted bid president Sebastian Coe.
Madrid came out top again, clearly ahead of Paris. London and New York trailed again - but the real loser was Moscow.
The Russian bid was awarded just 6.8 out of a possible 10 points, compared with Madrid's 8.5.
London has made much of its innovative venues for various sports - hosting the triathlon in Hyde Park, the beach volleyball on Horse Guards Parade and baseball in Regent's Park.
But the IOC complained: "No budget is allocated for upgrading or construction, or construction dates provided."
Madrid was rated the best, with Paris in second and New York third.
Another bad area for London.
The bid has made much of the proximity of the athletes' village to the proposed Olympic stadium - but the IOC criticised the distance between the village and the venues for events like shooting, sailing and canoeing.
Madrid and Paris both scored well - but New York's plans did not impress.
At last - a good area for London. The British bid scored as highly as any of the bids that were retained, largely because of its emphasis on regeneration of the East End.
Both New York and Moscow received low marks - but Paris and Madrid, the two front-runners, were rated as highly as London.
Paris, London and New York were all given maximum marks for their ability to provide enough hotel rooms to cope with the huge influx of visitors an Olympics would bring.
Moscow cemented its role as rank outsider with a low mark - and it is hard to see it being able to improve its rating in a mere six months.
London's worst area. The IOC said that the city's rail network was "obsolete", called for "substantial improvements in public transport" and said: "The assumed average bus travel speeds of 34mph appear unrealistic."
London's bid leaders claim that huge investments in transport are already planned - but the IOC remains to be convinced.
Madrid were awarded nine of a possible 10 marks and Paris 8, with the remaining three failing to score more than 6 apiece.
New York's plan to carry 85% of Olympic traffic on ferries on the East River was praised as "innovative" but there are doubts about its genuine feasibility.
SAFETY AND SECURITY
Paris leads the way, but London is close behind, let down only by the geographical spread of its venues, which the IOC say "could potentially entail complex planning for the security forces".
Moscow is rated poorly with New York only a small distance ahead.
EXPERIENCE IN HOSTING
Paris is the clear winner, having successfully hosted both the football World Cup in 1998 and last summer's athletics world championships.
London suffers from not having hosted a major event since the 1966 World Cup, and from having pulled out of hosting the 2005 world championships.
A key area, and one in which Moscow and New York again trail the other three.
London, Paris and Madrid were all praised for their financial plans.
PROJECT AND LEGACY
Once again, Paris and Madrid were out in front, both scoring nine points.
London and New York were awarded eight points each, reflecting the overall rankings, with Moscow again bringing up the rear.