The world's longest and deepest rail tunnel under the Swiss Alps is set to open shortly, ending 17 years of construction work. The Gotthard base tunnel, the design for which was conceived seven decades ago, is 57 km long and 2.3 km deep.

The tunnel will connect northern and southern Europe cutting under the Alps as Switzerland said the link would be a major breakthrough in Europe's freight transportation. French President Francois Hollande, German Chancellor Angela Merkel, and Italian Prime Minister Matteo Renzi are all set to be part of the inauguration ceremony on 1 June and will be among the first set of passengers.

Once the route becomes fully operational in December 2016, up to 260 freight trains and 65 passenger trains are expected to pass through the tunnel every day. Built at the cost of about $12bn (£8.28bn), construction of the tunnel began in 1999 after several rounds of bureaucratic delays and other concerns. Nonetheless, once approved, the completed project met the deadline and the original budget.

In 1992, the Swiss voted in favour of building a rail tunnel in a referendum on environmental concerns over freight transportation by road. According to the estimates of the Swiss federal railway police, the rail route would not only boost the freight service but also increase the current passenger rate of 9,000 to 15,000 by 2020.

"It is just part of the Swiss identity. For us, conquering the Alps is like the Dutch exploring the oceans," federal transport office director Peter Fueglistaler told Reuters.

The rail connection between Rotterdam in the Netherlands and Italy's Genoa was the end-product of the work of up to 2,400 workers. Over 28 million tonnes of rock was excavated during the construction process. At least nine workers were killed while on the job.

The Swiss tunnel beats Japan's 53.9km-long Seikan rail tunnel to become the longest in the world. However, it is still unclear how long the Swiss route will hold on to the record as the Chinese government said they have plans to build a similar rail tunnel of roughly up to 123 km.