Deep under the bowels of Stockholm runs a comprehensive underground system taking travellers quickly around the centre and out to the suburbs. Stockholm’s underground (Tunnelbana) dates from year 1933 and consists of three lines: blue, red and green with all lines passing through the middle point of T-Centralen, Central Station. The underground is a perfect way to get around in a city where the climate can be challenging for half of the year. However, being tucked under the earth doesn’t mean a lost opportunity. In fact, Stockholm’s underground is said to be the world’s longest art gallery with 90 of the 100 stations being decorated with mosaic, paintings or sculptures. The blue line is by far the most interesting with eye-popping Kungsträdgården, Solna and Rådhuset being of particular interest.