In the dark basement of the Manbij Hotel, Ahmad Othman stares defiantly into the room where he spent 32 days strung up by a chain, tortured by the "Islamic State of Iraq and the Levant" (ISIL) group.

"Our feet never touched the ground. Sometimes they pulled the chain up and down" to make the pain worse, Othman told AFP in the hotel-turned-prison that was run by ISIL in the Syrian town of Manbij.

"For a while after we were released, we could not walk or focus on anything anymore," he said.

In August, the Syrian Democratic Forces (SDF) -- an alliance of Kurdish and Arab fighters -- recaptured the town in the north of the war-wracked country.

In better times, the five-story Manbij Hotel once hosted foreigners and Syrians alike, who would come here on weekend getaways.

But during its two-year reign over Manbij, ISIL transformed the hotel into a nightmarish prison for anyone who violated the group's hardline interpretation of Islamic law.

Othman, a Syrian Arab in his thirties, spent three months there in late 2015 after being accused of collaborating with anti-ISIL fighters.

The former student of French literature was released following a lack of evidence against him -- and promptly joined the SDF.

Wearing his SDF fatigues, Othman returned with AFP to the hotel, which was heavily damaged in the airstrikes backing the SDF's offensive.

He entered the building slowly, peering around corners as if expecting an ISIL fighter to leap out and drag him back into captivity.

Forced into tiny containers

The hotel's lower floors were transformed by the jihadists into an underground maze of dark cells and torture chambers.

"The sun of the caliphate has risen," reads a hand-painted message on one wall.

"We definitely never saw any sun down here," Othman said bitterly.

Handcuffs still hang off the cells' black metal doors, with crudely cut-out slats allowing the jailers to keep an eye on their prisoners.

Orange-tiled shower stalls were turned into solitary confinement cells, and dust-covered clothing and plastic bottles still litter the floor.

In one room, metal containers under a metre high and 50 centimetres wide line the wall.

This was "where prisoners would sit for days until they confessed", said Othman, who spent several days himself squeezed into one locker-sized crevice.

He said detainees were only allowed brief intervals during which they could choose to eat or pray -- and those who opted to have breakfast instead of completing their morning prayers were beaten.

Othman then pointed to a row of rusted holes on a white tile wall.

"There used to be hooks here. This is where they would hang us," the bearded fighter said.

"They used to hit us everywhere, on our heads, our bodies.... They made us climb inside a large wheel that they would then hit."

Still, Othman considers himself lucky -- for managing to get out alive and in reasonably good health.

"Some stayed suspended in the air for six months. They can't walk at all any more because of blood clots," he said.

Others who were imprisoned with him were executed by ISIL.

"They just invent whatever accusation they feel like and behead people," Othman said.

"How do they dare call themselves an Islamic state?"