Before modern builders created the world's largest domes, ancient societies built domed structures in Mesopotamia, China, Persia, Greece and Rome.
One of the most famous domes from antiquity is the Pantheon, completed in 126 AD by Roman emperor Hadrian. It served as a Roman temple and, later, as a Catholic church. With a diameter of 43.3 meters, it is the largest unreinforced concrete dome in the world. A notable feature of the Pantheon is its coffered ceiling: The recessed panels serve to lighten its weight, a key factor in its durability.