Germany and Denmark are building the world's longest underwater rail and road tunnel | DW News

 At the Baltic Sea construction of the world's longest underwater rail and road tunnel is underway. The 18-kilometer passageway, due to be completed in 2029, will link Denmark and Germany. The €10 billion project crosses a stretch of the Baltic Sea known as the Fehmarn Belt and will have two double-lane motorways and two electrified rail tracks. The entire tunnel will be built using pre-fab concrete elements.