The new Gotthard Base Tunnel in Switzerland is the world’s longest train tunnel running at 57 km long under the Alps.

The world’s longest and deepest rail tunnel, Gotthard Base Tunnel, opened in Switzerland on Wednesday, nearly seven decades after it was first proposed and 17 years after construction began with a blast in the main shaft.

The Gotthard Base Tunnel is 57 km long (35-mile), and farther below ground than any other tunnel.

The $12 billion project was inaugurated by Swiss President Johann Schneider-Ammann.

“Today is an historic day for our country. We have completed the Gotthard Base Tunnel, an epic feat of engineering, a project that has involved generations, from the first sketches, to the planning and construction of the tunnel. I feel extremely proud, but also quite humble” said the prime minister speaking from the north portal in Rynächt, canton Uri.

Religious leaders blessed the tunnel; a statue of St. Barbara, the patron saint of miners, stands inside it. Nine workers who died while building the tunnel were honored on Tuesday with a bronze plaque. Five hundred passengers, selected from a lottery that 130,000 people entered, took part in the inaugural ride.

European leaders including German Chancellor Angela Merkel, French President François Hollande and Italian Prime Minister Matteo Renzi then made the trip on the first official journey on the line.

The high-speed rail running through the tunnel will make the train trip between Zurich and Milan about 45 minutes shorter, cutting it to 2 1/2 hours. Moreover, the amount of goods carried through the route is expected to increase to 260 trains daily from about 160.

For ten years, hundreds of workers braved tropical temperatures underground to get the tunnel finished. It has a system of two one-way tubes, linked by emergency escape routes every 325 metres.

When it opens for commercial service in December, the tunnel will remove thousands of polluting trucks from roads through pristine Alpine landscapes, NPR reported.

From first blast to opening celebration, the tunnel took 17 years to complete; nine people died in the process. “Engineers had to overcome crumbling rock and underground rivers they found along the way,” Eleanor says. “The entire Swiss nation was captivated by the project, following it every step of the way.”

The project, which cost more than $12bn (£8.3bn) to build, was endorsed by Swiss voters in a referendum in 1992. Voters then backed a proposal from environmental groups to move all freight travelling through Switzerland from road to rail two years later.

This immersive video tour gives a behind-the-scenes look at one of the biggest engineering feats in Swiss history.

(Video by Swiss Public Television SRF; English narration by Jo Fahy; additional editing by Carlo Pisani)