On the left of the picture: The Selimiye Mosque (mid-16th century).
On the right: The Mevlana Tekkesi complex. The original Seljuk buildings of it have been rebuilt or altered. The appearance of all (except the green tiled Türbe/Mausoleum of Mevlana) belongs to the reigns of Süleyman I (1520-1566) and Selim II (1566-1574) in the main.
Tekke = the largest kind of building (often a complex) designed specifically for gatherings of a Sufi brotherhood. It was a place for spiritual retreat and character reformation, and often served as hospices for Sufi travelers and Islamic students.
From Wikipedia: Sufism is defined by some adherents as the inner, mystical dimension of Islam, others contend that it is a perennial philosophy of existence that pre-dates religion, the expression of which flowered within Islam. A practitioner of this tradition is generally known as a sufi. They belong to different "orders" - congregations formed around a master - which meet for spiritual sessions, in meeting places known as zawiyah (zaviye), khanqah or (for the larger ones) tekke.
Correspondent: J.M.Criel, Antwerpen.
Sources: ‘Islamic Architecture: Ottoman Turkey’ (Godfrey Goodwin) – London 1977 & Wikipedia.