Copenhagen Tunnel
A tunnel immediately outside King's Cross Railway Station on the Great Northern Railway
The Copenhagen Tunnel is a set of three parallel railway tunnels carrying the main line tracks out of London's King's Cross terminus under the rising ground at Barnsbury, about a mile north of the station. Each bore has the capacity for two tracks. The eastern tunnel was taken out of railway service in the 1970s but is maintained to ensure the integrity of the ground overhead, and provides road vehicle access to Holloway Bank. The tunnel is just over 543 m (1,781 ft) long.
The first of the multiple tunnels was built as part of the construction of the Great Northern Railway and was opened in 1850. This section of the railway was designed by the engineer Thomas Brassey and was built by Pearce and Smith and John Jay. The name is taken from Copenhagen Fields, an open space directly above the tunnels, that was once the location of the Ambassador of Denmark's residence in the 17th century.
The original tunnel is now the middle of three parallel bores. A second tunnel to the west was built in 1877 and a third one to the east in 1886.
On 27 March 1849 the first brick for Copenhagen Tunnel was laid by Edward Purser.