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Øresund Link combines bridge, artificial island, and submerged tunnel under the sea between Denmark and Sweden, with 20 giant concrete blocks installed on the seabed to support an international crossing used by cars and trains.
Under the Øresund Strait, Denmark installed 20 giant concrete structures on the seabed to form a submerged tunnel integrated into the link that connects the country to Sweden by road and rail.
Each element used in the underwater passage measures 176 meters in length, 9 meters in height, and 40 meters in width, with a reported weight of 55 thousand tons per unit by Øresundsbron, the official administrator of the link.
Manufactured in a dedicated facility in Denmark, these pieces were then submerged on the seabed, where they became part of one of the least visible and most impressive sections of the crossing between Copenhagen and Malmö.
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Submerged tunnel under the Øresund Strait connects Denmark and Sweden
Between the Danish capital and the Swedish city of Malmö, the complex combines tunnel, artificial island, and bridge, creating an international crossing capable of accommodating cars and trains on one of the most well-known routes in Northern Europe.
According to the technical data released by Øresundsbron, the submerged section is 3,510 meters long and is completed by two portal buildings, each 270 meters in length.
These structures make the transition between the land part and the segment installed under the Drogden navigation channel, where the crossing disappears from the surface and continues below the sea.
Unlike tunnels drilled in rock, the technique used in Øresund does not consist of opening a continuous passage by excavation but in positioning large concrete elements within a dredged trench on the seabed.
Once aligned in sequence, these modules formed a submerged line capable of accommodating roadways and railway tracks, keeping the surface clear for maritime traffic in the Øresund Strait region.
55 thousand ton concrete blocks were aligned on the seabed
The scale of the pieces helps explain the impact of the work, as each block is longer than many large urban buildings and weighs the equivalent of tens of thousands of cars.
When they were fitted into the seabed, these elements created a hidden crossing under the water, allowing the international connection to function without turning the entire stretch into an elevated bridge over the sea.
According to Øresundsbron, the tunnel was designed with two tubes for road traffic, two railway tubes, and a service and escape tube, distributing the flows within the submerged structure.
This configuration separates cars and trains into their own corridors, while the service tube maintains an internal route focused on operational safety and technical access in situations foreseen by the project.
Under the Drogden channel, the presence of the tunnel meets a specific need of the region, as the solution avoids interference with the air traffic arriving and departing from Copenhagen Airport.
At the same time, the submerged passage allows large vessels to continue crossing the Øresund Strait, without the land and rail crossing blocking a strategic area for navigation.
Bridge, artificial island, and tunnel create hybrid crossing in Northern Europe
This combination makes the structure different from a conventional sea bridge because part of the route dives into the sea before re-emerging on land and continuing along the elevated connection towards Sweden.
In a single project, the design reconciled highway, railway, maritime navigation, and airport operation, creating a hybrid solution for an international corridor where different forms of transport share the same geographical space.
At the access to the road tubes, Øresundsbron reports that light filters were installed in the ceiling, a feature used to soften the transition between external brightness and the electric lighting of the underground part.
Internal safety also received its own solutions, including escape doors 1.2 meters wide every 88 meters, connecting the road tunnels to the service and escape tube.
To maintain operational conditions within the structure, each road tube also has 80 jet fans, whose main function is to remove smoke and heat in case of fire.
Besides this emergency role, the ventilation system helps preserve air quality during the normal operation of the crossing, especially in a closed structure that receives constant vehicle traffic.
Maritime engineering preserves navigation, airports, and land transport
Viewed from above, the Øresund connection became known for the contrast between its segments, as it seems to disappear into the sea on the Danish side, advance through an artificial island, and then continue as a bridge to the Swedish coast.
At the center of this engineering is the tunnel formed by the 20 concrete elements, a decisive part for the functioning of the crossing, although it remains hidden from those crossing the region on the surface.
Without this submerged solution, the connection would have to find another way to accommodate ships, planes, cars, and trains in a strategic area located between two European countries.
The navigation depth in the Drogden channel is reported by Øresundsbron as 10 meters, a fact that helps explain why the crossing needed to preserve a free maritime corridor.
Keeping this passage open allowed the operation of vessels without turning the entire connection into a sequence of elevated spans, a solution that would also need to coexist with the restrictions of the nearby airport.
Besides its transportation function, the Øresund tunnel draws attention for its assembly logic, based on the production, transportation, submersion, and fitting of monumental modules in a controlled maritime environment.
For the user, the transition between surface, tunnel, and bridge appears as a natural part of the journey, but the crossing depends on a sequence of giant structures installed where most people cannot see.
If 55,000-ton concrete blocks can be sunk into the sea to open a passage between two countries, what other mega-structures hidden under the water still go unnoticed by those who only see the surface?
