Construction has begun on what will be the world’s longest underwater road and rail tunnel, connecting the islands of Fehmarn in Germany and Lolland in Denmark. Although the countries share a land border further to the west, an 18km strip of the Baltic Sea currently makes travel between Copenhagen and northern Germany awkwardly circuitous. Once finished, the €7bn Fehmarnbelt Fixed Link, scheduled for completion in 2029, will almost halve the train-journey time between Hamburg and the Danish capital to just two and a half hours. To traverse the tunnel itself, trains will take just seven minutes and cars 10. The project has been in discussion since 1991 but work is finally underway on both sides of the border after a ground-breaking ceremony (pictured) in the German village of Puttgarden this week.