Alkis Konstantinidis/Reuters
An Iraqi soldier inside an office of the prison.
US-backed forces in Iraq are on the brink of taking back Mosul from ISIS.
The terror group's remaining militants in the city have sealed off the Grand al-Nuri Mosque - where ISIS leader Abu Bakr al-Baghdadi declared a caliphate in July 2014 - and are making their last stand.
The rest of the city has been liberated, giving journalists and US-backed forces a glimpse into what life was like under the Islamic State's rule.
One photographer recently visited an ISIS prison in the western part of the city, which had been built in an ordinary home to camouflage it among other houses. This is what he saw: