TOWERS AND DOMES

The Hagia Sophia is located in the country of Turkey, in the city that is now called Istanbul.

This city used to be called Constantinople,
because an emperor named Constantine named it after himself.
In the 6th - 7th centuries, the leader of Constantinople, who was called Emperor Justinian, commanded that 10,000 workers build him a Christian church.
The Hagia Sophia is the result.
It is called a Byzantine Church, since it was built in a period of time called the Byzantium.

It has a huge golden dome.
This church eventually became a Mosque, for people of the Muslim faith.
The towers on the corners, called Minarets were added when it became a Mosque.

What was the purpose of the Minaret towers on a Mosque?