The construction of the Hagia Sophia Church started in 532 and it was opened by Emperor Iustiniaus in 537. Since its erection, it has seen many repairs and additions. After the conquest of Istanbul, Mehmed the Conqueror established the Hagia Sophia Foundation. Following the conversion of Hagia Sophia into a mosque, a mihrab was built in the apse and a minbar was built next to it. It is stated in scientific sources that the minbar, muezzin mahfili (place of the assistant to the imam), four marble mahfils, preacher’s pulpit belong to the period of Murad III. However, İrteş argued that the features of the floral pattern behind the door of minbar belong to the Bayezid II period. This study will propose a dating based on the geometric patterns of the mosque.  

There are geometric patterns on the aforementioned building elements, and the analysis of these geometric patterns in the context of both the compass-ruler construction and the system behind them constitutes the basis of the study.

Hagia Sophia is an important building as it provides a basis for comparing pre-Islamic and post-Islamic geometric patterns. Based on the examples found in this mosque, the study will try to identify the reasons for the usage of the word “Islamic” in characterizing geometric patterns.

Looking at the historical process of geometric surface coating systems, it is possible to say that the intricacy of these systems is parallel to the development in science. In geometry, the 9th century was the period of translation and high scientific studies during the Abbasid period and is known as the period of “translation and transfer”. The first work translated in the field of geometry is Euclid’s Elements. Until this period, the geometric patterns in Islamic architecture were the continuation of the programme applied in the pre-Islamic buildings.  

In the period after the 10th century, which is called the “period of criticism and production”, geometric surfacing systems, like the developments in the field of geometry, were built with more complex structures. From then on, an artistic identity had started to be constructed with new designs in the Islamic process but taking its source from its past. The reason why geometric patterns are almost an identity is also the world of thought of that period, undoubtedly. 

The basis of the article is the analysis of all the geometric patterns applied in the mosque. These analyses will be performed with a compass-ruler construction. The geometrical structure behind the designs that sit on a correct structure constitutes scientific data. By dividing a corner angle into equal parts, patterns are classified by expressions such as fourfold, sixfold, etc. Or, as in the minbar, there are designs defined as a combination of four fold and six fold patterns on diagonally opposite corners.

In the Hagia Sophia Mosque, geometric surface coating systems are found on the Beautiful Gate, the omphalion and the entrance vault. However, these patterns are not complex patterns and they are the basis of the difficult patterns of the Islamic period. These patterns include square grid, isometric base or 8.8.4 semi-regular system. The geometric patterns on the surface of the Islamic architectural fragments placed after the church was converted into a mosque involve more compass-ruler movements than in the pre-Islamic period and require much more difficult problems to overcome.

Dividing an angle into three equal parts is an unsolved problem in the historical process. The design of the muezzin mahfil with its intertwined nonagons is related to this problem. For this reason we can analyze the pattern only by approximation.

The applications on the minbar are not in accordance with the technique of the mosques built during and after the Sinan period. The minbars of Sinan period are in openwork technique. In addition, the geometric design within the circular frame in the centre of the minbar, especially in Istanbul mosques, is generally in the category of five-fold designs. The minbars of Şehzade Mosque, Kara Ahmed Pasha Mosque, Valide-i Atik Mosque, Rüstem Pasha Mosque, Azapkapı Sokullu Mehmed Pasha Mosque, Edirne Selimiye Mosque, Mesih Pasha Mosque, Zal Mahmud Pasha Mosque and Kılıç Ali Pasha Mosque are good examples. The pattern on the minbar of the Gülnuş Valide Sultan Mosque, which is considered to be a work of the last classical period, is also in the openwork technique with rotational symmetry. However, all geometric pattern lines on the minbar of the Hagia Sophia Mosque were applied with relief technique and the lines are carved like Anatolian Seljuk geometric patterns with a weaving effect (lines passing from top to bottom).

The triangular side surface of the minbar has two triangular zones. In the small zone there is a combination of four fold pattern and six fold pattern. There are twelve-pointed stars, eight-pointed stars and between them five-pointed stars (not regular). The corner angle of these stars is 45 degrees. On the minbar of the Yavuz Selim Mosque (1522) there is the same pattern in the main triangular area.

The large triangular region in the minbar was applied in Al-Saleh Tala’i minbar in Cairo (1300) with wooden material. The pattern was applied in the main triangular area of the minbar of the Manisa Sultan Mosque (1522) in the same technique as in the minbar of the Hagia Sophia Mosque. The fact that the two patterns on the minbar were applied with a similar technique on the minbar of Yavuz Selim Mosque (1522) and minbar of Manisa Sultan Mosque (1522) suggests that the construction date of the Hagia Sophia minbar may be the end of the 15th century or the beginning of the 16th century.

In an analysis the “nizamî” (in accordance with the rules) of a geometrical pattern means that all the stars are bounded within a circle. The word “nizamî”, which entered the literature with this article, forms the backbone of the analysis.