Unusual subway

Sweden
Stockholm Metro is called "the longest art gallery in the world". The system is 110 km long and includes 100 stations.
Tunnels and huge station halls are carved deep into the salt rocks. Each station is decorated in its own way - some look like the fabulous grottoes of the underground kings, on others you can see Greek sculptures, corners of classical architecture, wall reliefs, mosaics or video installations, pop art is actively presented. Exhibitions are often held in the metro.