It began as a church in 537 under the orders of the Byzantine Emperor Justinian I, eager to go one up on his Roman antecedents by building a structure on an unprecedented scale.

BBC: An insider��s tour of Hagia Sophia

The Byzantine emperor Justinian is still known as "the Great" for reconquering Italy, north Africa and south-eastern Spain as well as codifying Roman law in a way which forms the basis of legal systems in many countries today.

BBC: A serious Justin at last