The Brazilian city, which failed to even reach the short-list when London were awarded the Games four years ago, was praised for its "excellent legacy plan" by the Evaluation Commission, who said that  it "is confident that the growing Brazilian economy would be able to support the necessary infrastructure development needed for the delivery of the 2016 Games".

Even what many thought could be a negative for the bid's hopes - the fact that Brazil is due to stage the FIFA World Cup in 2014, just two years before the Games would take place - does not worry the Commission too much.

They wrote in their report: "From a sponsorship perspective, the Commission expresses some concern about the ability of Games sponsors to fully activate their programmes in Brazil for a four year period, given the marketing activity surrounding the 2014 FIFA World Cup.

"Considering the potential of the growing Brazilian market, the increase in average household income and good ticket sales for major sports events, the marketing plan and revenue targets are considered to be achievable."

The city is also praised for its efforts in trying to improve security in the capital.

But the IOC do express concerns about the accommodation.

It said that 60 per cent of hotels which have provided guarantees have included a renegotiation clause in regard to rates, which the IOC warned "could represent a risk".

It also expressed concern over Rio's plans to house the media under its present plans, warning that it could struggle to "efficiently provide all the necessary services for such a major concentration of media in this village".

Chicago's bid is also widely praised for its vision and the quality of its venues but its lack of guarantees from the Government in Washington DC could undermine its chances.

The Report said: "Chicago 2016 has not provided a full guarantee covering a potential economic shortfall of the OCOG (Organising Committee of the Olympic Games), as requested by the IOC.

"Instead, it proposes a capped guarantee of USD 750 million (£462 million), presenting a risk for the IOC should the shortfall exceed this amount.
 

"At the time of the Commission’s visit, Chicago 2016 had formally requested the IOC to amend the Host City Contract.
 

"The Commission informed the bid that a standard Host City Contract applied to all cities."

The Report also expressed "some concern" that strongish winds in Chicago, universally known as the "Windy City" could disrupt competitions in archery, rowing, canoe, kayaking, tennis and open swimming.

Key failings, though, were identified in Madrid and Tokyo's bid by the Report, published in Lausanne. 

The Evaluation Commission, chaired by Morocco's former Olympic 400 metres champion Nawal El Moutawakel and which included Britain's Sir Craig Reedie, expressed concern at "the relatively low level of public support for a 2016 Games in Tokyo" in the IOC's opinion poll.
 

Only 55 per cent of Japanese polled nationally were in favour of the Games and only 56 per cent in Tokyo.
 

The Commission also criticised Tokyo for effectively misleading it.

 

The Report: "During the venue visits, it became apparent to the Commission that a number of venues listed as existing would in fact need to be built.

"This lack of clarity could have communications and legacy implications."
 

Meanwhile, the Report faulted Madrid's planned management and administrative structure, saying it "did not demonstrate a full understanding of the need for clear delineation of roles and responsibilities". 

It warned: "Given the current complexity and magnitude of delivering a major multi-sports event such as the Olympic Games, this could result in organisational and financial challenges."

It also expressed concerns over the the Spanish capital's plans for the Olympic Stadium, the rowing and open water swimming venues "could result in significant construction, operational and financial challenges".

The IOC will choose which city will host the 2016 Olympics at its Session in Copenhagen on October 2.

Read the full Evaluation Commission Report by clicking here.

Contact the writer of this story at [email protected].