The Metro is not only a convenient and efficient way to travel through Brussels, it's also a big museum.
In the 1960's, when the Metro line was being built, it was decided that, to avoid the blandness of an underground station, every stop would be made different and the project was to involve artists and architects to make every station an open and original space. And now, the Metro can be visited like a giant museum where art comes to you and where some people would take the metro just to have a look at those pieces of work. And Brussels really did do a great job getting many artists from different background to collaborate.
Because the lines and their extension where built at different times (from the '60s to late '90s), you'll find a great variety of styles.
Amongst my favourite: Paul Delvaux's fresco at the Bourse Station. When you know that trams are a recurring figure of this surrealist master, you can imagine that he was really happy to do this. Watch up: Pol Bury's sculpture is also quite worth a look.
Comic strips are big in Belgium that's why one of Belgium's most famous sons is immortalized in the Stockel station. I am talking about Herge's Tintin. Yes, the young reporter, his dog Snoway, Captain Haddock and the rest is in the metro. Sadly, Herge died before the completion of the work. He had the time to draw the plan before though.
Another big name is Francois Schuytten whose love for architecture is quite well-known. His books are often depicting a Brussels caught in the twilight zone. Familiar but at the same time creepy. Mixing the old Brussels and futuristic elements (read Brussel). His mold of an old tram that seems like appearing out of nowhere at the Porte de Hal station is a must-see.
Vic Gentils's "Aequs Nox"at the Thieffry station is quite spectacular and you won't be surprised to know it's been made in 70s. It represents a rising sun and it sure is shiny.
The Parvis de St-Gilles has the Universal Declaration of Human Rights written all over it, literally. The artist, Francoise Scheyn, has applied the same concept in cities like London, Berlin or Haifa. The station of Horta celebrates the architect who better represented Art Nouveau: Victor Horta with elements rescued from the destruction of the Maison du Peuple and Hotel Aubecq. Even the COBRA movement is represented with a painting by one of the movement leader, Pierre Alechinsky and Christian Dotremont at Anneesens. So... take the Metro and look around, beauty is all around, even underground.
Oh... you can also visit most of the stations on the STIB's website so, follow the link below.
For a virtual visit of art in the Metro: http://www.stib.irisnet.be/FR/51200F.htm. No English version available, sorry.