This week I'm working in Stockholm, and did not manage to get my usual cheap hotel near the office. Staying at the city center, I noticed a tunnel that I had not seen before: Brunkebergstunneln. A nice walkway from 1880s, 231 meters long.
It was also interesting to read about the construction of the tunnel from the Swedish wikipedia page. The construction was difficult due to soft ground materials. In the end they found a solution by using the freezing method of tunnel construction, freeze the ground in the tunnel during night, and then the day chip away a bit further and but concrete and steel to protect the tunnel from collapsing.
And it is a very convenient walkway for me to reach the metro stations.
Photos (c) 2018 by Jari Arkko. All rights reserved.