The world’s longest and deepest train tunnel officially opened on June 1 in Switzerland, nearly seven decades after the initial design was conceived and 17 years after its construction started. The opening saw the attendance of many European leaders as well as prayers by a priest, an imam and a rabbi, as well as colorful dance performances.

Switzerland’s 57-kilometre (35-mile) Gotthard Base Tunnel was constructed for 10 billion euros by a consortium, which also includes one subsidiary of Turkey’s Renaissance Construction in the country, Heitkamp Swiss. Major contractors for the project included Alpiq, Balfour Beatty and Thales, as well as Heitkamp.

The tunnel eclipses Japan’s 53.8-kilometer Seikan Tunnel as the world’s longest and bores deeper than any other tunnel, running about 2.3 kilometers (1.4 miles) underground at its maximum depth.

The project aims to cut travel times, ease roadway traffic and draw cargo from pollution-spewing lorries trucking between Europe’s north and south, according to the project’s website. The EU railway network will get a major boost from the shortcut through the Alps, notably on the route from Germany to Italy, with the opening of the tunnel.

260 freight trains, 65 passenger trains per day

When it opens for commercial services in December, the two-way tunnel will take up to 260 freight trains and 65 passenger trains per day. Journey time between Zurich and Milan will be cut by an hour thanks to trains passing through the tunnel.

The Gotthard Base rail tunnel is also being hailed as an environmental triumph as much as an unprecedented engineering feat across Europe.

According to the Swiss rail service, it took 43,800 hours of non-stop work by 125 laborers rotating in three shifts to lay the tunnel’s slab track.

At the peak of construction, as many as 2,400 workers took part in the project. The two holes were connected in October 2010, some 11 years after the first blast to build the tunnel, which took place in the last century.