The question of how to order our knowledge is as old as the systematic acquisition, circulation, and storage of knowledge. Classification systems have been known since ancient times and are often associated with a tree metaphor and visualisation. But visual representations of knowledge spaces are still an object for experts. A user navigating through large information spaces on-line is most of the time confined to a text based search interface and a list of hits as outcome. While increasingly more information is available on-line, navigating through it has not become simpler. This talk introduces ‘knowledge maps’ as means to visualise large collections of libraries, scholarly communication or your own personal information space. We also discuss why an alliance between communities as different as digital humanities, computer science, physics and sociologists of knowledge is needed to experiment, develop and implement knowledge maps.