Throughout human history, prisons have been places of punishment. The concept of a prison, as we have come to know it today, has not always been the same. Prisons have evolved from simple places for incarceration to instruments of punishment (where deprivation of liberty is the penalty for breaking the law), to settings for reform (where attempts are made to mould the guilty to conform to society's norms). The penitentiary systems developed by the penitentiary science have shaped the penitentiary system to the form it has today. The concept of reform and penitence is closely woven to the places it is sought in. Prison buildings have been evolving in parallel to the penitentiary system. After the middle ages, people turned to architecture in order to reform and redesign prison facilities. Dungeons were replaced by buildings specifically designed for these purposes. The architect, following penitentiary science guidelines, would design facilities whose structure and quality had only one purpose: To optimize the penitentiary system and the concept of penitence. A new kind of architecture had emerged: Prison architecture. Throughout the centuries, prison architecture has produced several models of prison buildings. Some of the designs have been successful, whereas others were not. Up to this day, architects are trying to redefine the relations between the facility and the prisoner or the facility and the city around it. On the 21st century, prison architecture takes a new form. Prison architecture is now leading changes in the penitentiary system, no longer a mere tool in the hands of penitentiary science. The principles that flow through prison architecture are now being put to the test. The architect designs the facility and the legislator wraps and shapes the legislation around it. History will tell if architecture will succeed in this path that it has taken.