The C City Central prison happens to be a maximum-security prison, where prisoners have close to zero chance of escape.
This prison houses most perpetrators of unspeakable crimes, dozens of death row prisoners, and prisoners with a lot of years to serve. One other group is those who are kept away from receiving visitors, as it may be detrimental to some persons of power.
As a result, they are kept in solitary confinement for the least negligible crimes, just to keep them away from their visitors. The duration of stay is also unreasonably long, but the warden's world is the prison, where he is the law.
The check at the entrance, through to the booth where prisoners were supposed to meet their visitors, was packed with one security device after the other. This means there are many checks to complete before reaching the final destination.
