St. Pauli Elbtunnel has enabled the people of Hamburg and its visitors to cross between Landungsbrücken at the northern habour and Elbe island for more than 100 years.

As well as being used by around 40,000 cars and a million pedestrians a year, its pipelines also carry fresh water through the 430-metre length underneath the River Elbe.

Now a historical landmark, the tunnel was built because ferry services couldn’t cope with the number of workers employed at the port, and today it is a protected monument.

With history comes degradation, and the refurbishment is a structural engineering challenge that is being taken on by the HPA - as you can see in this short video released by the Authority.