The ruins of Mosul

General view of destroyed buildings in the old city of Mosul. The United Nations estimates there are 10 million tons of rubble in Mosul overall, and the Old City�s streets are still knee-deep with debris. REUTERS/Alaa al-Marjani

Destroyed building from previous clashes in Mosul, January 2018. REUTERS/Khalid Al-Mousily

Students walk inside the damaged campus of the University of Mosul, February 2018. REUTERS/Khalid Al-Mousily

The destroyed al-Hadba minaret at Grand al-Nuri Mosque (L), June 2017. REUTERS/Erik De Castro

An old bridge destroyed by clashes is seen in the Old City, July 2017. REUTERS/Thaier Al-Sudani

The remains of al-Hadba minaret at the Grand al-Nuri Mosque in the Old City, July 2017. REUTERS/Erik De Castro

Destroyed buildings are seen in the old city, February 2018. REUTERS/Alaa al-Marjani

The remains of vehicles are seen in the Old City, June 2017. REUTERS/Alaa Al-Marjani

The destroyed al-Hadba minaret at the Grand al-Nuri Mosque, January 2018. REUTERS/Ari Jalal

Destroyed buildings in the Old City, July 2017. REUTERS/Thaier Al-Sudani

Members of the Emergency Response Division in the Old City, July 2017. REUTERS/Alaa Al-Marjani

Smoke billows from the ruined Grand al-Nuri Mosque after it was retaken by Iraqi forces, June 2017. REUTERS/Erik De Castro

A member of Iraqi Counter Terrorism Service (CTS) walks next to destroyed buildings in the Old City, July 2017. REUTERS/Thaier Al-Sudani

Military vehicles of Iraqi security forces in the Old City, July 2017. REUTERS/Alaa Al-Marjani

An old bridge destroyed during clashes in the Old City, July 2017. REUTERS/Thaier Al-Sudani

A member of Iraqi security forces holds an Islamic State flag in the Old City, July 2017. REUTERS/Thaier Al-Sudani