The crucial metro link to the Olympic Park in Rio de Janeiro was inaugurated Saturday in the presence of Brazil's acting President Michel Temer.
Temer was part of the first trip on the 16-kilometre line from the popular beach district of Ipanema to Barra where most of the venues have been built for the August 5-21 Games.
Countless delays and financial problems had raised questions over whether the line would be ready at all for the Games. At almost 3 billion dollars, it was the most expensive single project for the Olympics.
From Monday until Friday only accredited people such as athletes, team officials, the media and technicians can use the number 4 line. From then on ticket holders can use it as well.
The line will be open to the public after the Olympics and Paralympics are over on September 19, but will only be available for a few hours each day initially. Once in full operation, the line is expected to transport some 300,000 people per day.