Locat­ed at the cross­roads of sev­er­al trade routes from the 2nd mil­len­ni­um B.C., Alep­po was ruled suc­ces­sive­ly by the Hit­tites, Assyr­i­ans, Arabs, Mon­gols, Mamelukes and Ottomans. The 13th-cen­­tu­ry citadel, 12th-cen­­tu­ry Great Mosque and var­i­ous 17th-cen­­tu­ry madrasas, palaces, car­a­vanserais and ham­mams all form part of the city‘s cohe­sive, unique urban fab­ric, now threat­ened by over­pop­u­la­tion.