The Alhambra is a fortress and palace complex in Granada, Spain, which contains a fascinating array of designs and patterns. If we ignore the colours in the (slightly the worse for wear!) pattern above, we can see its repeating structure by, for example, drawing in the tessellation of parallelograms with star vertices. You can actually do this in many ways: can you see how? This design illustrates just one of the 17 possible wallpaper patterns: patterns differentiated by the groups of transformations mapping the patterns to themselves.
