The 200m-long, 4.5m-high structure will form the new coastline once the sea covers the front of the tunnel portal.

An outer, temporary dyke has kept the water out while the construction consortium Femern Link Contractors (FLC), comprising Vinci, Per Aarsleff, Wayss & Freytag, Max Bogl, CFE, Soletanche Bachy and BAM, has worked on the portal.

Bulkheads have been placed on the end of the tunnel facing the water and these can be removed from the inside after the first tunnel element is immersed and connected later this year.

Behind the dyke, work is continuing to finish the 260m-long tunnel portal.

The 18km-long immersed tunnel beneath the Baltic Sea will connect Rødbyhavn on Lolland in Denmark and Puttgarden on the German island of Femern. It will consist of 79 217m-long hollow, reinforced concrete elements and 10 special elements.