Markooh Fortress is cobblestone castle in south shore of the Caspian Sea, in Ramsar region, overlooking both sea shore and surrounding areas. It has an approximate length of 30 m, width of 18m and wall height of 6m. The castle originally belongs to Sassanid era (224-651 AD). In around 1100 the fortress was occupied by the powerful Hashashins, a faction of Ismailia Shia Muslims (known to the West as Assassins) for more than half a century. The fortress was frequently used by local rulers up to recent centuries