Prison

A correctional facility, detention center, gaol, jail, penitentiary, prison or remand centre is a facility in which inmates are forcibly confined and denied a variety of freedoms under the authority of the state as a form of punishment. Prisons are most commonly used within a criminal justice system; people charged with crimes may be imprisoned until they are brought to trial, those pleading of being found guilty of crimes at trial may be sentenced to a specific period of imprisonment. Beside their use for punishing civil crimes, jails and prisons are frequently used by authoritian regimes.

Security
Prisons are normally surrounded by fencing, walls, earthworks, geographical features or other barriers to prevent escape. Multiple barriers, concertina wire, electrified fencing, secured and defensible main gates, armed guard towers, security lighting, motion sensors, dogs and roving patrols may all be present depending on the level of security.

Modern prison designs have increasingly sought to restrict and control the movement of prisoners throughout the facility and also to allow a smaller prison staff to monitor prisoners directly; often using a decentralized "podular" layout.

Common Facilities
Modern prisons often hold hundreds or thousands of inmates, and must have facilities onsite to meet most of their needs including dietary, health, fitness, education, religious practices, entertainment and many others. Conditions in prisons vary widely around the world, and types of facilities within prisons depend on many intersecting factors including funding, legal requirements and cultural beliefs/practices. Nevertheless, in addition to the cell blocks that contain the prisoners, also there are certain auxillary facilities that are common in prisons throughout the world.

Political Prisons and Administrative Detention
Political prisoners are people who have been imprisoned because of their political beliefs, activities and affiliations. The category of "political prisoner" is often contested, and many regimes that incarcerate political prisoners often claim that they merely criminals. Others who are sometimes classified as political prisoners include prisoners who are politicized in prison and are subsequently punished for their involvement with political causes.

Many countries maintain or have in the past a system of prisons specifically intended for political prisoners. In some countries, dissidents can be detained, tortured, executed and/or "disappeared" without trial. This can either happen legally or extralegally. Administrative detention is a classification of prisons or detention centers where people are held without trial.

Psychiatric Facilities
Some psychiatric facilities have characteristics of prisons, particularly when confining patients who have committed a crime and are considered dangerous. In addition, many prisons have psychiatric units dedicated to housing offenders diagnosed with a wide variety of mental disorders.