For more than 1,000 years, the al-Hawza al-Ilmiyya south of Baghdad has been one of the hearts of Shi'ite Islamic scholarship, training the clerics who lead Shi'ite communities across the Muslim world.
Thousands of students, from teenage boys to university graduates, study Islam at its schools in the holy cities of Najaf and Kerbala.
Shi'ites, who are the majority in Iraq, were repressed under dictator Saddam Hussein, a Sunni Muslim, but now lead the Iraqi government since Saddam was overthrown in 2003. Clerics trained at the Hawza have wide social and political influence, both inside Iraq and abroad.
This year, around 200 fully fledged clerics will graduate, completing a process that requires at least ten years of study.
In the Najaf school, a typical day will see clerics in flowing black robes and white turbans giving lectures to groups of students sitting on the floor of a great hall, lined with pointed arches and elaborate mosaics.
For a photo essay on the life of student Shi'ite clerics, click here: http://reut.rs/2wQATVE
Students are given instruction in subjects including Islamic jurisprudence, philosophy, theology, logic and interpreting Islam's holy book, the Koran.
The Kerbala school teaches around 250 students each year, and in Najaf there are more than 1000. Together they are served by a faculty of around 90 teachers.
"Hawza has a high rank at the heart of the society," Wael Noor Al-Deen Murtadha, a Shi'ite cleric and lecturer at the school, told Reuters.
"What is important about Hawza is that it reduces the moral degeneration and irregularities of life. It creates a culture among people aimed at reinforcing social relationships between different sects away from any discrimination."