Geometric proportions in Islamic architecture: case of the Sidi El Bena mosque in Tlemcen

The mosque of Sidi El Benna is one of the Islamic buildings of Tlemcen built up during the Zianid era. In this study its planes, facades and sections were drawn based on different measurements, because this style is characterized by the use of geometric proportions. In the next step the measurements of heights, widths, lengths and angles of different architectural elements were compared in order to find arithmetic and harmonic proportions. The last ones were found especially in the golden number Φ, equal to 1.618. In addition, the cubit of time was computed and found equal to 0.4375 m, almost equal to the Roman one - 0.444 m. Other principles of geometric composition, such as repetition and symmetry, were also identified.