The Mundaneum tells the story of Paul Otlet and Henri La Fontaine, two Belgian visionaries who in the 1890s attempted to organise all human knowledge into a single, universal index. Their system used index cards and a hierarchical classification scheme called the Universal Decimal Classification, which is still used in some libraries today. At its peak the collection contained 12 million entries.
The museum is small but genuinely fascinating — part history of information technology, part portrait of a particular kind of early 20th-century idealism that believed the world could be improved through the systematic organisation of facts. The exhibits cover Otlet's life and the project's rise and fall, including its destruction by the Nazis in 1940. The building itself, a converted Art Nouveau warehouse, is worth seeing in its own right.