Hundreds of thousands of people formed a 'human mosaic' in Madrid to show their support for the city's bid to host the 2016 Olympics.
The human mosaic was formed five days before the International Olympic Committee makes its decision.
The IOC is to announce in Copenhagen on Friday whether Madrid, Rio de Janeiro, Chicago or Tokyo will host the 2016 Games.
The Madrid 2016 organizing committee planned the event, which they called an "Olympic fiesta", to show the "strength of support" among residents for the city's candidature.
The city councilor responsible for crowd safety, Pedro Calvo, said that around 400,000 attended the gathering in the Plaza Cibeles, where supporters of Real Madrid traditionally celebrate its titles. The organizers put the figure at half a million.
The crowd formed the human mosaic by holding up cards of the different colors of Madrid's candidature, red, green, blue and yellow.
"What happened today is very important for Madrid's bid, because we have sent a strong message not only to the IOC members but to the entire Olympic movement that this city loves sport and wants the Games," said Madrid Mayor Alberto Ruiz-Gallardon.
The Madrid organizing committee has regularly pointed to the strong popular support in Spain for Madrid's Olympic bid as one of the arguments for holding the Games in the Spanish capital.
Also Sunday, 2,016 golfers set a Guinness world record by hitting golf balls at the exactly the same moment in an event near the capital.
A Spanish delegation of several hundred people is to leave for Copenhagen on Monday, headed by King Juan Carlos and Prime Minister Jose Luis Rodriguez Zapatero.