Built between 1884 and 1886, this tunnel was built to shorten the journey through the Brunkeberg esker (glacial ridge) for pedestrians and cycles. The tiunnel is 231 metres long and 4 metres wide. At its deepest it is around 40 metres beneath ground level.
During construction, the western part the soft esker bedrock proved unstable. A freezing machine from England was hired to freeze the soil to -18 Celsius to be able to dig it out.
The spot where Tunnelgarten - the approach road to the tunnel - meets Sveavägen a hundred or so metres away achieved notoriety on 28 February 1986 when Prime Minister Olof Palme was assassinated.