The Old City is a 0.9-square-kilometer (0.35 sq mi) walled area within the modern city of Jerusalem. The history of the Old City has been documented in significant detail, notably in old maps of Jerusalem over the last 1,500 years. This area constituted the entire city of Jerusalem until the late 19th century; neighboring villages such as Silwan, and new Jewish neighborhood such Mishkenot Sha'ananim, later became part of the municipal boundaries. The Old City is home to several sites of key religious importance: the Temple Mount and Western Wall for Jews, the Church of the Holy Sepulchre for Christians, and the Dome of the Rock and al-Aqsa Mosque for Muslims. It was added to the UNESCO World Heritage Site List in 1981. Traditionally, the Old City has been divided into four uneven quarters, although the current designations were introduced only in the 19th century. Today, the Old City is roughly divided (going counterclockwise from the northeastern corner) into the Muslim, Christian, Armenian, and Jewish Quarters. The Old City's monumental defensive walls and city gates were built in 1535–1542 by the Ottoman sultan, Suleiman the Magnificent.