Immediately to the east of the Dome of the Rock lies an enigmatic building known as the Dome of the Chain. It is one of the most ancient buildings on the Haram and was either built during the Umayyad period or, some think, prior to Islamic rule in Jerusalem. Reasons given for its construction and its date are varied. Different theories based on comments in medieval sources echoes in the work of contemporary scholars.
Rosen-Ayalon was the first to notice that the building is located in the precise center of the Haram, a fact which might indicate that the building refers back to the days of the Jewish temple or at least to the traditions that surrounded it. This link is also expressed in medieval sources that associate the Dome of the Chain with the site where David hung a chain that could not be grasped or touched by anyone deceitful, unjust or wicked. It is also said that this is the place where Solomon, the son of David, administered justice. Another source refers to it as the place of the 'Holy of Holies' (the most sacred and inaccessible place in the Jewish Temple), which is thought of in Jewish tradition as the omphalos, the navel of the universe. In Islamic tradition the omphalos is assigned to the Ka`ba in Mecca and Christian tradition often recognizes this prominent and powerful spot at the site of the Holy Sepulchre.
Most researchers assign the building to Abd al-Malik who built the Dome of the Rock and may have started to build the mosque of al-Aqsa. It is interesting to indicate that the mihrab in the mosque of al-Aqsa is located exactly in the middle of the qibla wall of the Haram on north-south axis with the Dome of the Chain. Some scholars and travelers in past and present conceived the Dome of the Chain as bayt al-mal, the treasury for the local Muslim community. But the completely open shape of the building seems to defy this theory. The building is usually pictured in Islamic tradition as the spot where the Final Judgment will occur in the end of days and where a chain will stop the sinful and let the just pass through.
The unusual shape of the structure is a composition of a domed hexagon with open arches surrounded by an eleven-sided polygon with eleven open arches. It is the third largest building on the Haram after the mosque of al-Aqsa and the Dome of the Rock with a diameter of 14 meters.
Sources:
Rosen-Ayalon, Myrian. 1989. The Early Islamic Monuments of Al-Haram al-Sharif: An Iconographic study. Jerusalem: Qedem, 25-29.
Grabar, Oleg. 1996. The Shape of the Holy: Early Islamic Jerusalem. Princeton: Princeton University Press, 130-131.