RAQQA -- Militias declared victory Tuesday in Raqqa, the city the Islamic State of Iraq and Syria (ISIS) considered its capital. But it came at a terrible price, CBS News' Holly Williams reports.

Williams walked into the heart of the city, now reclaimed -- after a four month battle -- by U.S.-backed fighters, who took Williams to al-Naim Circle. It's a place where ISIS showcased its brutality. A photo of a jihadi young son captures their depravity.

What ISIS did in al-Naim Circle was designed to terrorize -- not just the people in Raqqa who witnessed it in person but anywhere that people saw their photos and videos on the internet.

To get rid of the extremists, they've destroyed the city, leaving hardly a building unscathed. U.S. coalition airstrikes have flattened many of them, and inadvertently killed civilians, according to survivors.

A woman is shown at a cemetery in Raqqa. CBS News

Buried beneath the rubble, people may never know for sure how many died.

Rojda Felat, who was the commander of the Raqqa offensive, said the city will be rebuilt. But the extremists did damage that can never be repaired.

Ahmed Hamdi escaped Raqqa two months ago, he said. But as he evacuated the city, an ISIS bomb tore off both his legs and killed his wife.

"I want to kill hundreds of them," he said.

At a Graveyard north of Raqqa, people came to pay their respects to the hundreds of U.S.-backed fighters who have died in battle, a war that has cost people the lives of their sons and daughters.

Three years after the U.S.-led coalition began its bombing campaign against ISIS, the group is coming close to losing all of its former territory in Syria and Iraq. But that doesn't mean the end of ISIS, and as far as we know, the strikes haven't killed the group's leader, Abu Bakr al-Baghdadi.