The remains of a mihrab in an exterior wall of the Allaeddin Camii. Seljuk or early-Ottoman, 12th-15th century.

The purpose of prayer niches in exterior walls of mosques is related to ritual prayer during Ramadan (turkish: ‘Ramazan’). During that Islamic month of fasting, some prayers (on Friday, for example) are attended so massively, that not all worshippers find a place inside the prayer house. Those who don’t, gather in the courtyard (or on the street); the exterior mihrabs help them feel connected with the people inside.

From Wikipedia: Mihrab (Arabic: محراب‎ miḥrāb, pl. محاريب maḥārīb) is a semicircular niche in the wall of a mosque that indicates the direction of the Kaaba in Mecca and hence the direction that Muslims should face when praying. The wall in which a mihrab appears is the "qibla wall."

Correspondent: J.M.Criel, Antwerpen.