The shamsa was a ceremonial crown that formed part of the regalia of the Abbasid and Fatimid caliphates. It consisted of a gigantic suspended crown made of gold or silver and studded with pearls and precious stones. It was based on the ceremonial crown that was similarly suspended over the head of the Sasanian king. Under the Abbasids, the shamsa symbolically represented the absent caliph during the official hajj observances while the amir al-hajj was personally in charge of the pilgrim caravan. Once the pilgrims had reached Mecca, the shamsa would be hung up in front of the ka'ba during the hajj ceremonies.