In the centre of Raqqa is the main football stadium.
They are holding victory celebrations here at the moment but throughout Islamic State's reign of terror it was synonymous with death.
People brought here rarely left.
A group of soldiers told me to follow them over rubble into the bowels of the building to understand the sheer horror of the place.
The prison was discovered just days ago
The soldiers said it was the prison of death as I scrambled down into a long dark corridor.
They said the first section was for women. Further down it was for men.
:: The rise and fall of Islamic State in Raqqa
This was a vast prison complex they said could hold between 500 and even thousands at a time.
People were suspended from these beams and beaten
The prison cells are of different sizes - some large to accommodate groups of prisoners, others tiny breeze block chambers a few metres square.
One was a tiny box for extreme punishment.
Discovered just days ago, the prison felt dreadfully unsafe as we worked our way through it. The soldiers told me to keep to hard surfaces and avoid anything in a sack lying on the floor.
In some of the cells the condemned had written messages to their families on the walls.
A final goodbye.