Aleppo is located in northern Syria. The region, which sits on the boundary between the Arabian geologic plate and the African plate, is part of the Dead Sea Fault system. In the early 12th century this ancient Muslim city was home to tens of thousands of residents. On Oct. 10, 1138, a small shock shook the region, and some residents fled to surrounding towns. The main quake occurred the following day. As the city walls crumbled, rocks cascaded into the streets. Aleppo’s citadel collapsed, killing hundreds of residents.
Although Aleppo was the largest community affected by the earthquake, it likely did not suffer the worst of the damage. European Crusaders had constructed a citadel at nearby Ḥārim, which was leveled by the quake. A Muslim fort at Al-Atārib was destroyed as well, and several smaller towns and manned forts were reduced to rubble. The quake was allegedly felt as far away as Damascus, about 220 miles (350 km) to the south. The Aleppo earthquake was the first of several occurring between 1138 and 1139 that devastated areas in northern Syria and western Turkey.