All these pictures were taken at the Etnographic Museum near the Blue Mosque and Blue Türbe.

‘Seccade’. Prayer rug (meaning: with the design of a ‘mihrab’ in its center).
West-Anatolian (Gördes, Manisa), 18th century. Knotted pile technique (wool, Turkish knot).
Also called ‘Transsylvanian’ (or: Siebenbürgen) by European collectors.

This very popular class of rug is misleadingly named after the eastern European province (in nowadays Romania), into which it was imported in large quantities during the 16th and 17th centuries. The principality of Transsylvania (called ‘Siebenbürgen’ in German) lies in the curve of the Carpathian mountains and was at the time tributary to the Ottoman empire. These Anatolian prayer rugs were later used to decorate Transsylvanian churches, where many examples can be seen to this day.

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.
Source: ‘Catalogs of Turkish Handwoven Carpets’– Turkish Ministry of Culture (for identification).