The mainly white-stoned old town was built within the historical walls of the city, pierced by the nine historical gates, while the newer quarters of the old city were first built by the Christians during the early 15th century in the northern suburbs of the ancient city, after the Mongol withdrawal from Aleppo. The new quarter known as al-Jdayde is one of the finest examples of a cell-like quarter in Aleppo. After Tamerlane invaded Aleppo in 1400 and destroyed it, the Christians migrated out of the city walls and established their own cell in 1420, at the northwestern suburbs of the city, thus founding the quarters of al-Jdayde. The inhabitants of the new quarters were mainly brokers who facilitated trade between foreign traders and local merchants. As a result of the economic development, many other quarters were established outside the walls of the ancient city during the 15th and 16th centuries.