The Fehmarn Belt Fixed Link is an immersed tunnel set to link the Danish island of Lolland with Germany's Fehmarn island. This remarkable tunnel beneath the Baltic Sea, expected to become one of the world's longest underwater structures, is due for completion by 2029.

Spanning 18 kilometres (11 miles), the Fehmarnbelt tunnel will drastically reduce journey times between Scandinavia and mainland Europe. Femern described the tunnel as "Denmark's largest infrastructure project and the world's longest immersed tunnel and rail link".

The project carries an estimated price tag of DKK 55.1billion (£6.4billion), with the European Union providing approximately 1.3billion euros (£1.1billion) in funding.

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Femern outlined that an immersed tunnel represents a "safe, tested and efficient way of building an underwater tunnel".

"The technology is Danish-developed and builds on experiences from, among others, the Øresund Tunnel. Once completed, the tunnel will not pose any obstacle to vessel traffic in the Fehmarnbelt. Marine safety is also a top priority during the construction phase.

"The Fehmarnbelt tunnel will be just as safe as a corresponding section of motorway above ground. The tunnel is equipped with continuous hard shoulders and emergency exits along its entire length."

The Institution of Civil Engineers highlighted that the Fehmarnbelt Tunnel will rest atop the seabed, marking it as "a remarkable engineering feat". "Weighing in at 73,500 tonnes apiece, these colossal structures are a testament to modern engineering. Once a tunnel element is ready to be shipped, waterproof bulkheads (barriers) are installed at both ends, and the segment is carefully towed into position by tugboats.

"In total, 89 elements will be connected sequentially - much like assembling giant Lego pieces - to form the complete tunnel."