The Great Belt Bridge (Storebæltsbroen), properly the Great Belt Fixed Link, is the 18-kilometre (11 mi) road and rail crossing of the Great Belt strait between the Danish islands of Zealand and Funen. It uses the small island of Sprogø in mid-strait as a stepping stone: a suspension bridge, the East Bridge, carries the motorway from Halsskov on Zealand to Sprogø, with twin rail tunnels running beneath the same channel, and a low box-girder bridge, the West Bridge, carries both road and rail on to Knudshoved on Funen. The East Bridge’s main span of 1,624 metres (5,328 ft) was the second-longest in the world when the link opened to trains in 1997 and to cars in 1998. It cost an estimated DKK 21.4 billion at 1988 prices, making it the largest construction project in Danish history. It replaced ferries that had crossed the Belt since 1883 and joined the two halves of Denmark.
A 60-kilometre strait between Zealand and Funen
Denmark is split by water. The Great Belt (Storebælt) is the largest of the three Danish Straits through which the Baltic Sea drains to the Kattegat and the open Atlantic; the other two are the Øresund between Zealand and Sweden and the Little Belt between Funen and Jutland. The Great Belt is about 60 kilometres (37 mi) long and between 16 and 32 kilometres (10 to 20 mi) wide, and it wraps around Samsø in the north and Langeland in the south.
The strait is young in geological terms. It began as a river, called the Dana River by geologists, cut about 9,000 to 8,900 years ago when the freshwater Ancylus Lake in the Baltic basin lost its outlets near Gothenburg and drained southward instead. As sea levels rose, salt water broke through along the Dana River’s course, turning the lake into the Littorina Sea and the river valley into a seaway.
What the strait divides matters as much as its size. On the eastern side is Zealand, at 7,031 km² (2,715 sq mi) the largest island of Denmark proper, with Copenhagen and 2,319,705 people on 1 January 2020, about 40 per cent of the country. On the western side is Funen, 3,099.7 km² (1,196.8 sq mi) with 469,947 people in 2020 and the city of Odense, and beyond it the Little Belt and the Jutland peninsula, Denmark’s land link to the rest of continental Europe. Any route between Copenhagen and Germany, Jutland or the rest of the continent by land had to cross the Great Belt somewhere.
Sprogø, the stepping stone
The geography also offered a solution. Almost exactly halfway across the strait, 6.7 kilometres (4.2 mi) from the Zealand shore and 8 kilometres (5 mi) from Funen, lies Sprogø. At this point the Great Belt divides around the island into an East Channel and a West Channel, which meant that one enormous crossing could be broken into two. The island has a long history as a waypoint: archaeologists working ahead of the bridge found traces of people more than 8,000 years old, King Valdemar the Great built a fortress there in the twelfth century, and its name, recorded in the twelfth century as Sproøe, appears to mean “scout’s island”. In 1868 a lighthouse was built on the foundations of Valdemar’s fortress. To carry the link, the island was drastically reshaped: land reclamation enlarged it from 38 to 154 hectares (94 to 381 acres). It has no permanent residents today and is a nature reserve used by Sund & Bælt, the company that runs the crossing.
Ice in 1658, ferries from 1883: crossing the Belt by Korsør and Nyborg
For most of history the Great Belt was crossed by boat, and at least once on foot. In the exceptionally cold winter of 1658, during the Little Ice Age, King Charles X Gustav of Sweden marched his army across the frozen Little Belt to Funen and then, from 5 February, across the ice of the Great Belt by way of Langeland, Lolland and Falster, reaching Zealand on 11 February. With Swedish troops 22 kilometres from Copenhagen, Denmark made peace, and the Treaty of Roskilde signed on 26 February 1658 handed Scania, Blekinge, Halland and other provinces to Sweden.
The modern crossing began with the railway. The first train ferries, H/F Korsør and H/F Nyborg, entered service on 1 December 1883 between the harbour towns of Korsør on Zealand and Nyborg on Funen, linking the railway lines on either shore; the state railway company DSB, created in 1885, ran them for more than a century. Cars came later: after motorists complained about high prices and cramped conditions, the first automobile-only ferry, M/F Heimdal, entered service in 1930. Post-war car traffic overwhelmed the route, and on 28 May 1957 road traffic moved to a new ferry service between Halsskov and Knudshoved, about 1.5 kilometres north of the old one and connected to a new motorway. Those two headlands later became the landfalls of the fixed link.
Before the link opened, an average of 8,000 cars a day used the ferries. A crossing took around 90 minutes on average, including waiting at the ports, and much longer at weekends and holidays. Plans for a bridge had appeared as early as the 1850s; DSB proposed one in 1934, and a government commission studied the idea from 1948. Parliament passed a first fixed-link law in 1973, but the project was frozen in 1978 when the Venstre party demanded cuts in public spending. Political agreement came in 1986, a construction act followed in 1987, and building started in 1988.
Why the East Channel needed a 65-metre-high suspension bridge
The two channels on either side of Sprogø are not legally the same. Denmark long forced foreign merchant ships to use the Øresund and pay the Sound Dues there; when it gave up the toll, the 1857 Copenhagen Convention opened Danish waters, and the eastern half of the Great Belt became an international waterway. The western half, between Sprogø and Funen, is Danish territorial water. That distinction helps explain why the two halves of the crossing look so different.
Across the West Channel, Denmark could build low. The West Bridge (Vestbroen), built between 1988 and 1994, is a concrete box-girder bridge 6,611 metres (4.1 mi) long with 18 metres (59 ft) of clearance for ships. It is really two bridges side by side on shared foundations below sea level, the northern one for the railway and the southern one for the road, with 63 deck sections resting on 62 pillars.
Across the East Channel, the main shipping lane into the Baltic, it could not. Here the road crosses on the East Bridge (Østbroen), a suspension bridge built from 1991 to 1998 and designed by the Danish firms COWI and Ramboll with the architects Dissing+Weitling. It is 6,790 metres (4.2 mi) long, with a central span of 1,624 metres and 65 metres (213 ft) of vertical clearance. Its two pylons reach 254 metres (833 ft) above sea level, the highest points of any self-supporting structure in Denmark, and nineteen concrete pillars set 193 metres apart carry the approach spans. Even 65 metres was contested: in 1991 Finland took Denmark to the International Court of Justice, arguing that Finnish-built mobile offshore drilling rigs would no longer fit under the bridge. The two countries settled for DKK 90 million in compensation and Finland withdrew the case in 1992. Denmark had hoped the East Bridge would be the world’s longest suspension span, but construction delays meant Japan’s Akashi Kaikyō Bridge opened about two months earlier.
The trains go underneath. The East Tunnel (Østtunnelen) is a pair of bored tubes, each 8,024 metres (5 mi) long, linked by 31 cross passages at 250-metre intervals that house the rail equipment and serve as escape routes. Boring them was the hardest part of the job. During construction the seabed gave way and one tube flooded; the water reached Sprogø and ran into the second, still dry, tube, damaging two of the four boring machines, though no one was hurt. Engineers laid a clay blanket on the seabed so that the tunnels could be pumped dry, and most of the boring was then done from the Sprogø end, especially after a fire in June 1994 stopped the machines on the Zealand side. Rail traffic, planned for 1993, began in 1997; road traffic followed in 1998. Seven workers died in work-related accidents during construction.
Building in a strait also meant protecting it. Under the so-called zero-solution, the bridge was not allowed to reduce the flow of water between the Baltic and the Kattegat, so parts of the Great Belt were dredged to widen the cross-section and compensate for the piers and ramps. Monitoring concluded that flows are now almost what they were before. On 2 January 2019 a semi-trailer fell from a freight train on the West Bridge and hit a passenger train travelling the other way, killing eight people.
Halsskov to Knudshoved in ten minutes: how the link reshaped Denmark
Once the link opened, the strait shrank from a 90-minute ferry trip to a 10- to 15-minute drive. Traffic jumped 127 per cent in the first year as people made journeys they had never bothered with before. In 2021 an average of 34,100 vehicles a day crossed, and on 7 August 2022 a record 61,528 vehicles passed in 24 hours.
The railway changed just as much. Trains no longer had to be short enough to fit on a ferry, so DSB’s seating capacity across the Belt on an ordinary Wednesday rose from 11,060 to 37,490 seats, and the fastest Copenhagen–Odense journey now takes 1 hour 15 minutes. Combined with the Little Belt bridges and the Øresund Bridge, built between 1995 and 1999, the link created an unbroken road and rail line from continental Europe through Denmark to Sweden, and freight trains between Sweden and Germany gained an all-rail route, although limited rail capacity means some of that traffic still goes by ferry. In 2009 seven wind turbines with a total capacity of about 21 MW were put up in the sea north of Sprogø to supply the link. The next big change will come from the south: the Fehmarn Belt Fixed Link on the Rødby–Puttgarden route to Germany, expected by 2028, will shorten the Hamburg–Copenhagen rail journey and take some international traffic away from the Great Belt.
To see how the eastern half of this route continues to Sweden, read our guide to the Øresund Bridge. For the Japanese suspension bridge that beat the East Bridge to the record by two months, see the Akashi Kaikyō Bridge, and for the city at the Zealand end of the journey, try our profile of Copenhagen.