Government that attempted to reestablish centralized power were called what?

The correct answer is: Hagia Sophia

Explanation:

Hagia Sophia is the former Orthodox Christian cathedral in Istanbul (ex Constantinople), Turkey, built in 537 AD.

The church was dedicated to the holy wisdom of God. Until 1453 it was the Orthodox congregational church of the Ecumenical Patriarch,  except between 1204 and 1261 when it was converted into a Catholic Church during the Latin Empire.

In 1453, the Ottoman Empire conquered Constantinople and Mehmed II ordered that the church be converted into a mosque. The building was a mosque from 1453 to 1931 when it was secularized and converted into a museum.

It is the most famous example of Byzantine architecture, famous for its massive dome and it was the world largest building of that time.