The London Underground: A metaphor for explaining IA

I've been meaning to read Jason Hobbs' description of what IA's do using the analogy of the design of wayfinding maps and signage for the London Underground. His nine photo examples are where the metaphor comes to life. Jason draws examples from the design system employed throughout the Underground to illustrate how information architecture should be similarly interested in using design and structure to help users in their journey through information space. Great stuff.