The aim of the research is to develop the preliminary architectural design of a medium-sized penitentiary for older male inmates, which meets the target audience, legislation, regulations and the overcrowding of current prisons. In which architecture works on the personality of inmates in the process of reintegration into society, with implementation in the city of Xanxerê. The study was carried out in the form of descriptive bibliographical research and the method used was deductive, based on analysing case studies. To this end, the scope of the project's location was studied, as well as the need for a penitentiary to serve the region of the Alto Irani Association of Municipalities. It was considered that the current prison needs support in meeting demand, thus improving the quality of the penal execution system in the western region of the state of Santa Catarina, justifying the need for this project. In order to assess the feasibility of setting up the prison, the surrounding area, road system and infrastructures were taken into consideration, as well as climatic, physical and legal constraints, and an on-site survey was carried out to assess the location.