The world's longest railway tunnel was inaugurated in Switzerland by Swiss President Johann Schneider-Ammann, who highlighted the significance of the project for Europe.
"Epic achievements are still possible in Switzerland and in Europe," he said before the first two trains carrying 1,000 citizens entered the 57-kilometre Gotthard Base Tunnel.
Ammann said the tunnel would bring Europe's economies and peoples closer together.
The Gotthard Base Tunnel in central Switzerland, which cost 12.2 billion Swiss francs (12.3 billion dollars), was designed to boost environmentally friendly cargo traffic on rails across the Alps and to better connect industrial hubs in Germany, Switzerland and Italy.
It took 17 years to build the structure which replaces Japan's 53.9-kilometre Seikan Tunnel between Japan's Honshu and Hokkaido islands as the world's longest rail tunnel.
Specators at the opening ceremony were treated to a mostly sombre spectacle featuring and alphorn players and actors playing evil mountain spirits, as well as clowns and acrobats representing various regions of Switzerland.
Guests at the opening ceremony included the leaders from neighbouring countries: German Chancellor Angela Merkel, French President Francois Hollande, Italian Prime Minister Matteo Renzi and Austrian Chancellor Christian Kern.
The first two trains that will cross underneath the Saint-Gotthard mountain range in the early afternoon will carry 1,000 ordinary citizens, in a symbolic gesture to the Swiss taxpayers who footed the bill for this project.
National Swiss railway SBB plans to open the tunnel for regular rail traffic on December 11, after conducting final test drives over the coming months.
Although Switzerland has finished the Gotthard tunnel, it will not be used at full capacity for years, as Italy and Germany have yet to complete railway infrastructure projects on routes feeding into Switzerland.
German Transport Minister Alexander Dobrindt promised Wednesday to push efforts to increase cargo traffic heading through the new tunnel.
Germany had already invested 2 billion euros (2.2 billion dollars) to expand the railway line in the Rhine valley and had earmarked an additional 6.5 billion euros for the project, he said.
"We will also work just as fast to expand the other lines flowing to the Gotthard tunnel," he said on the sidelines of the Swiss ceremony.