The mosque is the Ayazma Mosque, built 1760 by Sultan Mustafa III and dedicated to his mother. It is in a baroque style, and has some great ornaments that I did not hesitate to take pictures of. Also, it has several "houses" on its walls, meant for pigeons.
On the picture: The ‘kitabe’ (building inscription) above the main entrance to the prayer hall of the mosque.
Late-Ottoman, dated 1174 H. (1760 AD). The calligraphic text is written in sülüs script, and is the work of Şeyhülislâm Hattat Veliyüttin.
Sülüs (from Arabic: ثلث ṯuluṯ "one-third"), also referred to as ‘thuluth’, is a script variety of Islamic calligraphy invented in Persia, which made its first appearance in the 11th century AD. The straight angular forms of the older Kufic script were replaced in the new script by curved and oblique lines. In Sülüs, one-third of each letter slopes, from which the name (meaning "a third" in Arabic) comes. It is a large and elegant, cursive script, used in medieval times on mosque decorations.
Correspondent: J.M.Criel, Antwerpen.
Sources: ‘Türkiye Tarihi Yerler Kılavuzu’ – M.Orhan Bayrak, Inkılâp Kitabevi, Istanbul, 1994 & Wikipedia.