One of the oldest and largest castles in the world, the Citadel of Aleppo, has reopened for visitors following the liberation of the northern Syrian city from militants in December, as shown by footage on Saturday. ~ Russian soldiers were amongst the the first tourists to take in the sights of the Citadel together with locals from Aleppo. The Citadel is a part of the Ancient City of Aleppo, which has been a UNESCO (United Nations Educational, Scientific and Cultural Organization) World Heritage Site since 1986. Usage of the Citadel has been traced back to at least the 3rd millennium BC.