The network map of the London Underground is often put forward as a good example of information visualisation. Certainly this style of metro map has been adopted in many cities to assist train travellers understand the various routes and network connections. This paper reports on a preliminary investigation into the question: Can the metro map metaphor be adapted for effectively displaying more abstract knowledge? Four case studies are described that use the metro map metaphor for presenting abstract, interconnecting "trains of thought". These four case studies include using a metro map to summarise the ideas in a complex thesis, using a metro map to communicate a business plan, using a metro map as navigation aid for web pages and using a metro map to assist university students understand a course structure. This paper discusses the aspects of these abstract metro maps from an information visualisation perspective. Experiences learned from the case studies are used to introduce some issues and guidelines for using this metaphor to help people find their way through more abstract data.