The Fehmarn Belt is a 50km (31 miles) stretch of water separating Denmark and Germany. Turns out that Germany is Denmark’s second biggest export market. Denmark has a high-speed rail network but even that takes over 5 hours to get from the capital to the Danish side of Fehmarn. Freight trains take even longer.

So the logical next step to speed up trade is to build an underwater tunnel linking the closest points between Denmark and Germany. The idea of constructing a fixed transport network between Denmark and Germany is over 100 years old.

Initial ideas included a 3km bridge, but it was eventually ruled out due to unstable soil conditions and extreme technical challenges. In the end, boring a tunnel under the Fehmarn Belt was the most economical if ambitious solution.

YouTuber The B1M AKA Fred Mills travels to Fehmarn, Germany and Denmark to take a look and in the process educate and inspire future budding engineers.