The 57-kilometre tunnel will cut the journey from Zurich to Milan down to two hours and forty minutes, an hour less than before.
Regular rail service through the world's longest and deepest tunnel has opened in Europe. The Gotthard tunnel is over 57km (35-miles) long and runs through the heart of the continent, connecting Switzerland and Italy.
It took 17 years to build the tunnel that cuts to 17 minutes the time it takes for high-speed trains to now cut through the Alpine mountain range that divides Europe's north and south.
TRT World's Shamim Chowdhury has the story.