Inside the Fehmarnbelt Tunnel: Europe’s 18 km undersea mega-link set to transform travel between Germany and Denmark

The Fehmarnbelt Tunnel is an 18-kilometre submerged undersea tunnel that will directly connect Germany and Denmark beneath the Baltic Sea. It is one of Europe’s most ambitious infrastructure projects and is set to become the world’s longest submerged undersea tunnel. The tunnel is being built under the Baltic Sea. Once completed, travel between the two points will become easier.At present, it takes approximately 60 minutes to cross the Baltic Sea. After completion of the tunnel, the same distance will be covered by train in just seven minutes.

The tunnel is not being constructed using traditional digging methods. Instead, large sections are being built and then submerged into the sea. In May 2026, the project reached a significant milestone when the first massive segment of the tunnel was successfully installed in place.
The first segment measured 217 metres in length and weighed approximately 73,000 tonnes. Installing such a structure underwater required precise engineering work. The segments were placed with extreme precision, with an error margin of only 3 millimetres.Construction of the Fehmarnbelt Tunnel began in 2020 on the Danish side and in 2021 on the German side. The project is expected to be completed by 2029. It will strengthen the connection between Germany and Denmark. The Fehmarnbelt Tunnel could add a new chapter to Europe’s transportation network.