This publication describes the fortress of Qal'at al-Bahrain. The fortress, dating from the beginning of the Islamic period, had been discovered in the north of the island of Bahrain. It aroused the interest of archaeologists working on the Islamic world. This site appeared to be related to the Umayyad fortified residences on the Syro-Palestinian steppe and was the first to be discovered outside the area of origin of this caliphate dynasty.