This is the Koca Mustafa Paşa complex. It's mosque is a former church, St. Andrew in Krisei. Inside are some good capitals, the light was too low to take their picture.Nearby is the shrine of the famous Istanbul folk-saint Sümbül Efendi, who was the first sheik of the dervish tekke which was established here in the 16th century.

Another shrine at the same complex.

On the picture: This is the cenotaph sarcophagus of Sümbül Efendi; it is surrounded by a gilt brass grid in Late-Ottoman style. The grave monument still attracts many pilgrims, more specifically those related to the Halveti Brotherhood, of which Sümbül Efendi was an important leader.

The Khalwati Order (or Halveti, as it is known in Turkey) is an Islamic Sufi brotherhood (tarika). Along with the Naqshbandi, Qadiri, Mevlewi and Shadhili orders, it is among the most famous Sufi orders. The order takes its name from the Arabic word khalwa, meaning ‘method of withdrawal or isolation from the world for mystical purposes.’ The order was founded by Umar al-Khalwati in the city of Herat (western Afghanistan). However, it was Umar's disciple, Yahya Shirvani, who founded the “Khalwati Way.” The Halveti Order is known for its strict ritual training of its dervishes and its emphasis of individualism. Particularly, the order promoted individual asceticism and retreat, differentiating themselves from other orders at the time.

Correspondent: J.M.Criel, Antwerpen.
Source: Youtube canal of Sinaneddin Yusuf & Vikipedia.