"his most eminent prisoners were lowered into the depths of the Carcer and garrotted"

The sign outside the Carcer records that this is the place where St.Peter and St.Paul were held.
GNU Free Documentation LicenseThe sign outside the Carcer records that this is the place where St.Peter and St.Paul were held. - Credit: Maltesedog/Wikimedia Commons
The Carcer was a prison in the Forum Romanum in Rome, where it appears that high profile prisoners were kept.