I remember first coming across the idea of mental maps, maps that reflect how we perceive and negotiate the environment around us, rather than reflect real space or concrete spatial relationships as a geography undergraduate. I like this TED talk by graphic designer and cartographer Aris Venetikidis that elegantly describes how we mentally process space and movement through it and applies these concepts to the chaotic muddle of public transport in Dublin, The results are elegant, meaningful visualizations of movement through the real and mental space of Dublin. Impressive.