This is what ISIS' longest-held city looked like after years of occupation

Some of the streets were in disarray.

Debris piled up.

Buildings were destroyed.

Some areas of the city looked completely abandoned.

This mosque was damaged.

Some walls were blown out.

But still, Iraqi Security Forces celebrated in the streets after ISIS was driven from the city.

Iraqi forces made their way through the city and observed what was left behind from ISIS' brutal rule.

They found this weapons factory.

And a school filled with explosives.

The militants left behind rocket-propelled grenades on a desk underneath a Dora The Explorer illustration in this school.

Iraqi forces also found books belonging to the militants. ISIS has been known to create and publish propaganda books, including textbooks for children.

This room was used as a prison.

Prisoners were kept in these cages.

Iraqi-government-allied Shia fighters, who were supposed to stay out of the city center while the fight for Fallujah was ongoing, inspected abandoned sites.

The city's liberators found signs left behind by ISIS, which the group used to intimidate the populace into obeying its strict laws.

Here, security forces posed for a photo in front of murals ISIS had painted with themes of violence.

The militants also built underground tunnels around Fallujah, as they have in other areas under ISIS control.