This basilica, considered the epitome of Byzantine architecture, was completed in 537 AD by Emperor Justinian I. It was the largest cathedral in the world for one thousand years, and it has been said to have "changed the history of architecture." It is known as A) the Vatican. B) the Pantheon. C) the Hagia Sophia. D) St. Peter's Cathedral.

The Hagia Sophia, its construction consists of mostly masonry. The structure is composed of brick and mortar joints that are 1.5 times the width of the bricks. The mortar joints are composed of a combination of sand and minute ceramic pieces displaced very evenly throughout the mortar joints. This combination of sand and ceramic pieces could be considered to be the equivalent of modern concrete at the time.

From the date of its construction completion in 537 until 1453, it served as an Eastern Orthodox cathedral and the seat of the ecumenical patriarch of Constantinople, except between 1204 and 1261, when it was converted by the Fourth Crusaders to a Roman Catholic cathedral under the Latin Empire. The building was later converted into an Ottoman mosque from 29 May 1453 until 1931. It was then secularized and opened as a museum on 1 February 1935. It remained the world's largest cathedral for nearly a thousand years, until Seville Cathedral was completed in 1520.

The Hagla Sophia.

Explanation: This structure is viewed as one of the greatest religious artifacts in the world.