Mark Wallinger, Labyrinth, London Underground Tube Stations, London "You learn to know where people want to go even if they don't know themselves," one tube employee at Bank station told me, as I wandered around the labyrinth of tunnels, escalators, and platforms in search of Mark Wallinger's own Labyrinth - artwork number 142 out of 270. These black designs on white vitreous enamel are small enough - about the size of a TV - to blend in with the underground atmosphere of signage, so that they are often impossible to find unless you are assisted by the very friendly, informative, and sometimes bemused staff. Each design is a variant on a circular labyrinth with a red cross at the bottom, marking the single entrance, which doubles up as an exit. The point about the labyrinth is that there is only one path; once you are in, it's very difficult to get out. Wallinger has been commissioned by Art on the Underground to commemorate the 150 anniversary of the tube. By the summer, there will be a Labyrinth in all 270 stations; at the moment, there are 23. Winner of the 1995 Turner Prize, Wallinger, 53, grew up in Chigwell, Essex, 100 yards from the Central Line. He said recently that Harry Beck's original tube map is such a part of our collective identity as Londoners that it is internalised, "mapped onto one's mind." This might be true, but I have lived in London all my life and I still have to check the tube map to see where I'm going. Perhaps the familiarity makes it difficult to remember where things are. The simplicity of the designs is a nod to the mythic overtones of the labyrinth, as opposed to the maze, which is more commonly associated with garden hedges. The single path that leads you back to where you started is symbolic of the idea of a return. Rather than a grand quest, this commute is "a daily ritual for most people," as Wallinger points out. The resonance of these works lies not so much in the designs themselves, but in the act of trying to find them. To search for this quasi-existential map transforms the tube stations into destinations in their own right. Rather than using the stations to get from A to B, Labyrinth is a fun exercise in getting lost. It draws attention to the Dickensian surrealism of London, which appears stuffed with mad people of all descriptions.