Key Facts

• Denmark and Germany are building a very large tunnel under the Baltic Sea.
• When finished, the tunnel will be the longest made-for-roads-and-trains tunnel in the world.
• This tunnel is 18 kilometers (or 11 miles) long.
• The sections of the tunnel are being made at a factory and then placed on the sea floor.
• The project cost about €7.4bn ($8.1bn; £6.3bn). Most of this money came from Denmark and €1.3bn was given by the European Commission.
• When the tunnel is finished, a car drive or train ride between Rødbyhavn in Denmark and Puttgarten in Germany will take just 10 minutes.
• The new railway will also make the travel time between Copenhagen, Denmark, and Hamburg, Germany, half as long.
• The tunnel builders are a Danish company called Femern.
• The builders use special equipment and careful methods to put the tunnel sections in the right place under the sea.