This is not a talk on astrophysics of star formation, but on geometry, on how the central stars of the Arabic mosaics of the Alhambra are created.

The mosaics of The Alhambra are beautiful examples of tessellation of the plane, most often with a 6, 8, or 12-pointed star as central motif. In this talk I will discuss the geometric basis of the Alhambra mosaics, their symmetries, and the formation of their central star or polygon. I will also show the step-by-step graphic construction of the mosaics by means of the program code "mosaic".

In addition to the Alhambra mosaics, I will also show some other Arabic mosaics from the Alcazar de Sevilla, the Great Mosque of Cordoba, Morocco, India, and also roman mosaics from Empuries and modern-style floor tiles from Barcelona.