The Emtsai Synagogue or Middle Synagogue, (Hebrew: בית הכנסת האמצעי), also known as the Kahal Tzion Synagogue, forms the central chamber of the complex. It was originally a courtyard which probably used as the women’s section of the Rabban Yohanan Ben Zakai synagogue. During Sukkot it could be converted into a sukkah for the worshippers. With the growth of the community, it was decided during the middle of the 18th century to roof the yard. It was turned into what is today known as the Middle Synagogue, due to its location in the "middle" of the other three synagogues.
Read more about this topic: Four Sephardic Synagogues