Visitors walk inside Aleppo's ancient Grand Umayyad mosque in the old city of Aleppo, Syria, on Oct. 6, 2010.
Debris liters the Grand Umayyad mosque, on Dec. 15, 2013.
Syrian pro-government forces walk in the Grand Umayyad mosque after they captured the area on Dec. 13, 2016.
After weeks of heavy fighting, regime forces were poised to take full control of Aleppo, dealing the biggest blow to Syria's rebellion in more than five years of civil war.
The Old City of Aleppo as seen from Aleppo's historic citadel on Dec. 11, 2009.
The Old City of Aleppo and Aleppo's historic citadel on Oct. 12, 2016.
Restoring full control over Aleppo, Syria's most populous city before the war, would be a major prize for Syrian President Bashar al-Assad.
People tour Aleppo's historic citadel on Dec. 11, 2009.
A general view shows damage to Aleppo's historic citadel, which is controlled by forces loyal to Syria's President Bashar al-Assad, on Oct. 1, 2014.
The remains of a shell outside Aleppo's historic citadel on Dec. 13, 2016.
The war has killed hundreds of thousands of people, driven more than half of all Syrians from their homes and created the world's worst refugee crisis.
PHOTOS: Syrians Flee Besieged City