A trip on Stockholm’s tunnelbana, the city’s underground rail system, is no ordinary journey. Most of the network’s stations – more than 90 – have been transformed from purely functional spaces into galleries of art.

In a project that began in the 1950s, commissioned artists used murals, mosaics and installations to theme each station. Some artists were inspired by history. Some created statements about the environment or human rights. Others strived simply to bring calm to a space that often is not. The result is a subterranean world of keyboards on ceilings and rainbows on rocks.

Stockholm’s underground art is surprising and fun. And yours to enjoy for nothing more than the price of a local train ticket.