Istanbul, Tokyo and Madrid have handed over their bid files to host the 2020 Olympics and Paralympics to the International Olympic Committee.
IOC members will make a decision on who will host the games by secret ballot in Buenos Aires in September.
The bid documents, which run to several hundred pages, reveal plans for all key areas for hosting the Games including venues, budgets and security.
"Madrid is perceived as low risk, but Spain's struggling economy cannot be ignored. Tokyo is also seen as a safe prospect. One of the main reasons it lost out for the 2016 Games was a lack of public support in Japan, an issue the team members have tried to address. Istanbul, with its unique selling point of an Olympics spanning Europe and Asia, and a relatively strong economy has been seen as an early frontrunner. But with just over eight months until the final decision, nobody really knows who the 100+ IOC voters are going to pick. Today marks the start of an exhausting push for support, which will take the bid leaders all over the world."
The files are to be made public by the bid cities on Tuesday.
The IOC's evaluation commission, led by Britain's Craig Reedie, will visit the cities in March and prepare a report for members in June.
The 15-member executive board, headed by IOC president Jacques Rogge, chose the three finalists after examining a technical evaluation report compiled by a panel of Olympic experts in May 2012.
They decided to drop Qatar's Doha and Azerbaijan's Baku
from the shortlist.
Japan's Tokyo hosted the Olympics in 1964, while neither Istanbul in Turkey nor Spain's Madrid have held the Games.
Madrid is bidding for a third consecutive time, Tokyo a second time in a row and Istanbul a fifth time overall.
Italian capital Rome pulled out of the running in February 2012 because of the country's efforts to head off a debt crisis.
Brazil's Rio de Janeiro will stage the 2016 Olympics and Paralympics.