The Hindenburgdamm Causeway
It was opened in 1927 exclusively for rail transport. The crossing took about six hours in adverse weather and flow conditions lasted longer. Because the situation was unacceptable, the causeway re-routed entirely through Germany. For the first 45 years of its existence the Hindenburgdamm had a single track. In 1972 it was widened and a second track was laid.