After an official opening ceremony at 3pm, all stations were opened an hour later and residents and visitors in the city headed into the new Metro line.

Both Queen Margrethe and Prime Minister Mette Frederiksen gave speeches as part of an opening ceremony at City Hall Square. Photo: Philip Davali/Ritzau Scanpix

Comprising 17 new stations, 15.5 kilometres long and linking the three ‘bridge neighbourhoods’ (Vesterbro, Nørrebro and Østerbro) with the central station and City Hall Square, the new M3 City Ring Metro line significantly expands the reach of the underground train.

Photo: Philip Davali/Ritzau Scanpix

Photo: Philip Davali/Ritzau Scanpix

The City Ring is expected to double the number of passengers who use the Metro within its first year of operation, with a total of 122 million journeys expected by the underground rail in 2020.

The Copenhagen public was keen to try out the new transport. Photo: Ida Marie Odgaard/Ritzau Scanpix

Photo: Philip Davali/Ritzau Scanpix

It has been described as the biggest construction project in the Danish capital since the time of King Christian IV, who built many of the city's historic buildings and much of the Christianshavn area in the 17th century.

The project has not been without controversy, in particular in relation to its reported use of imported construction workers on wages lower than Danish standards. Photo: Philip Davali/Ritzau Scanpix

The new Metro line took just under 10 years to build at a cost of 25.3 billion kroner (3.4 billion euros).

Photo: Philip Davali/Ritzau Scanpix

READ ALSO: Copenhagen's new Metro line is a black spot for phones