The team of experts charged with scrutinising the hopefuls -- Madrid, London, New York, Paris and Moscow -- will fly into the Spanish capital on the first leg of a journey which will go a long way towards deciding which bid is successful.
Over the next seven weeks, the commission will spend four days in each candidate city. The winner will be announced at the International Olympic Committee's session in Singapore on July 6.
The 12-strong team, led by Morocco's 1984 Olympic 400 metres hurdles champion Nawal El Moutawakel, will meet bid leaders and city and government officials during the visits. Its findings are due to be published in May.
IOC members have been barred from visiting bid cities since the Salt Lake City voting scandal in 1998 and 1999.
The team will visit Madrid from February 3-6, London from February 16-19, New York from February 21-24, Paris from March 9-12 and Moscow from March 14-17.
The commission has already analysed the cities' weighty bid books, or candidature files, which pinpoint every last detail of their proposals to host the Games. These hefty tomes were submitted last November.
The five cities looking to take over the Olympic mantle from Beijing, the host city in 2008, will now be pulling out all the stops to ensure their commission visit runs like clockwork.
However, an Olympic city needs more than just nuts and bolts and it is the can-do spirit and feeling on the ground that the team will be looking to absorb on their trips.
Although the commission's report will carry a lot of weight, voting IOC members do not have to abide by any of its recommendations.
Sources close to the selection process believe the vote in Singapore will be one of the closest ever, and so the smallest detail could prove key.