Underground Mosque
The Underground Mosque or Kurşunlu Mahzen is a mosque located in the Beyoğlu district of Istanbul, Turkey. Its exact year of construction is unknown. According to Evliya Çelebi, it was built in the year 92 AH (711 AD) by Ömer, son of Abdülaziz, and later converted into a mosque. It appears in Ottoman official records under the name Mahzen-i Sultani. Some sources refer to it as a fortress named “Kastellion ton Galatau.” It was built during the reign of Tiberius II (578-582) to control the entrance to the Golden Horn against the increasing Arab raids. In Cristoforo Buondelmonti's engravings, dated to the first half of the 15th century, the castle consists of a courtyard surrounded by high walls and a tall tower, and is also the place where one end of the chain blocking the entrance to the Golden Horn was attached. Galata Hisarı / Mahzen-i Sultani is not visible in the 1573 drawings by Matrakçı Nasuh and the 1584 drawings by Hünername.
