At a ceremony at Casa Brasil in Somerset House to mark the landmark, Carlos Nuzman, the President of the Rio 2016 Organising Committee, said: "Four years from now, the Olympic cauldron will be lit at the Maracanã Stadium and the Omega watch will be telling us it is show time.

"This may seem a long time off, but we are already experiencing the Games as if they were taking place today.

"After all, we have a lot of work to do every day: decisions to make, tasks to complete and people to bring on to our team."

Nuzman was joined by Leonardo Gryner, the chief executive of the Organising Committee, and Stephen Urquhart, the President of Worldwide Olympic Partner Omega, who have supplied the countdown clock for Rio 2016 present in Casa Brasil in Somerset House (pictured top).

Work is currently ongoing on Rio's Olympic Park, which will cover an area of 1.18 million square metres, and host nine sports during the Games.

The foundations of the Olympic Village have also been laid, and the design for the golf course for the sport's Olympic debut already selected.

Work is also being carried out to renovate the iconic Maracanã stadium which is being rebuilt for the World Cup Brazil hosts in 2014.

The stadium will host the Opening and Closing ceremonies of Rio 2016, as well as some football matches.

Carlos Nuzman (left) and Stephen Urquhart at the Rio 2016 fours years to go ceremony

Rio will feature seven competition centres in four Olympic regions of Rio: Barra, Deodoro, Maracanã and the world famous Copacabana.

There are 152 observers from Rio 2016 here in London to learn from these Olympic and Paralympics.

Nuzman said that Rio was experiencing the benefit of learning from London's experience in putting on this summer's Games, which have just a week to go until the Summer Olympic baton is handed to him and his team.

"We know that we are dealing with the most complex project that exists," he said.

"You could feel that here in London.

"The 2016 Games are Brazil's Games, not just Rio's.

"With four years to go, we continue to learn and be inspired here, and at the same time, we are making significant progress in our home town.

"We can already feel the transformational power of the Rio 2016 Olympic and Paralympic Games in a very tangible way."

The Rio Games will be the first time the Olympics have been held in South America.

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