A transformative engineering feat is taking shape beneath the waters between Denmark and Germany: the Fehmarnbelt Tunnel. This undersea tunnel, spanning 18 kilometres (11.2 miles), is set to become the world’s longest road and rail tunnel, and the longest “immersed” tunnel ever constructed. The tunnel will carry two lanes of road traffic and two electrified rail lines, significantly cutting travel times across one of Europe’s busiest shipping routes.
The tunnel will reduce the current 45-minute ferry journey between Denmark and Germany to just 10 minutes by car and 7 minutes by train, making trips between Hamburg and Copenhagen much faster. Construction, estimated at €7.4 billion ($7.7 billion), reached a major milestone in February 2025 with the completion of the first precast concrete sections. These sections are 217 metres long and weigh 73,000 tonnes each, equivalent to 10 Eiffel Towers.
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Scheduled for completion by 2029, the tunnel is expected to boost tourism and enhance eco-friendly travel across the region. However, environmental concerns remain, with the overseeing company Femern A/S taking measures to mitigate the ecological impact by creating natural areas to offset potential harm.
Once completed, the Fehmarnbelt Tunnel will stand as a modern engineering marvel and an essential link in Europe’s transport infrastructure.
