Final answer:
El Salvador built a supermax prison, a highly secure type of prison meant for the most dangerous individuals, with strict controls and limited freedoms for inmates.
Step-by-step explanation:
The type of prison that was built in El Salvador is a supermax prison, designed to house the most dangerous prisoners and those deemed as high escape risks. Unlike minimum security prisons, a supermax prison features extremely tight controls, extensive surveillance, and very limited freedoms for inmates. This level of security is significantly higher than what is found in standard maximum security prisons or general correctional facilities. Supermax prisons are part of a broader debate around the purpose and effectiveness of severe incarceration measures, which include concerns about recidivism and the potential roles of rehabilitation and penal reform.