As UNESCO meets in Saint Petersburg to discuss which beauty spots to include on its list of world heritage sites, one architectural treasure in Syria is under grave threat. The Crac des Chevaliers castle in Homs province was built between 1142 and 1271 during the time of the crusades and the fortresses are once again being put their defensive use. In Arabic, the site is called Qal'at al-Hosn which means the impregnable fortress. Syrian rebels have been holed up amid the ruins for several months and are fending off a concerted onslaught from government troops. The fighting is fierce and shells rain down at regular intervals. And yet the strategic fortress is still standing, but at the cost of many lives. The inhabitants of the town of Azzara, which lies at the foot of the Crac des Chevaliers know that if the fortress's defences break, they will be subjected to the full force of the regime's artillery power and will have to flee for their lives, just like the inhabitants of the Baba Amr neighbourhood of Homs. Duration: 01:48