Question: What is a significant mosque in Istanbul, made of two former Eastern Orthodox churches and a chapel,  Istanbul High School, or Zeyrek Mosque?
Sentence (from "Zeyrek Mosque"): Zeyrek Mosque (full name in Turkish: "Molla Zeyrek Camii" ) or Monastery of the Pantocrator (in Turkish: "Pantokrator Manastırı" ), is a significant mosque in Istanbul, made of two former Eastern Orthodox churches and a chapel.
Relevant evidence: Yes