Where was the world's longest train tunnel in 2016?

After almost 20 years (started construction on 4 November 1999 and completed construction on 1 June 2016), Switzerland officially opened the world's longest and deepest rail tunnel.

The 57km (35 miles) twin-bore Gotthard Base Tunnel (GBT) provides a high-speed rail link under the Swiss Alps (the western Glarus Alps and the central Lepontine Alps at the eastern Gotthard Massif) between northern and southern Europe. The GBT starts in Erstfeld, canton of Uri (north, 460 m (1,510 ft) and the last stop is at End Bodio, canton of Ticino (south, 312 m (1,024 ft).

With the GBT, Switzerland revolutionized European freight transport.

Goods that were previously carried on roadways by millions of heavy-duty trucks for years are now going by train instead.

The GBT overtook Japan's 53.9km (33.49191 miles) Seikan rail tunnel as the longest in the world and pushed the 50.5km (31.37925 miles) Channel Tunnel linking the UK and France into third place.