A once-in-a-generation construction project is set to transform travel between central Europe and Scandinavia. When completed in 2029, the $8 billion Fehmarnbelt tunnel will be both the longest combined road and rail tunnel and the longest immersed tunnel anywhere in the world.

Officially known as the Fehmarnbelt Fixed Link, the 11-mile-long tunnel linking Germany and Denmark will sit in a trench at the bottom of the Baltic Sea at a depth of up to 130 feet.

It’s a key component in the development of the Scan-Med corridor, a transportation network that spans more than 3,000 miles from Malta in the south to Finland in the north. Along the way, it tunnels through Alpine mountains and crosses oceans. But approaching Scandinavia, a stretch of water known as the Fehmarn strait causes a 300-mile detour for both road and rail traffic on the north-south route.

The planned rail link will reduce travel time from Hamburg to Copenhagen from five hours to less than three hours, while the road link will replace a heavily-trafficked ferry service and reduce travel time by about one hour.

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