The Assad legacy is one of horror, hundreds of thousands dead, millions displaced, or in exile.

But perhaps nothing illustrates the deep depravity more than the atrocious archipelago of prisons and torture centers,

where tens of thousands were killed by the regime.

Special correspondent Leila Molana Allen takes us inside some of these now liberated

hells on earth as Syrians search for answers and for their loved ones. And a warning,

this story contains many images and accounts of violence.

The word that has struck terror into the hearts of every Syrian for decades, said Naya.

A black hole of pain and abuse where tens of thousands disappeared.

Few ever emerged again.

But now those who feared these walls have breached them,

desperately searching for survivors of deposed President Bashar al-Assad's

nightmarish Damascus prison.

A sudden swarm. They've heard a sound.

This group of family members and fighters have found a steel wall, and they think they can hear voices behind it.

They're searching now trying to break through to see if there may be any prisoners behind it still alive.

Rescue crews have been searching the vast mountain compound for days, following rumors of a network

of hidden cells underground. Pounding through layers of concrete, they found nothing. But with tens

of thousands more detainees still missing, these families are holding

on to that fading hope. And everyone here is determined to leave no stone unturned.

Outside, more crowds and pleading faces. Malak's 16-year-old son was taken seven years ago. She never

heard from him again, but the

government told her he was alive in jail.

...