Opened in 1985, the Sonora Regional Museum is in Hermosillo's Old Prison, facility that was closed in 1979. The building is a magnificent structure of the Porfiriato, on the slopes of the Cerro de la Campana, and largely built from stone extracted from these mountains. During the restoration and fitting out of the prison only those elements were removed which altered the original appearance from the time it operated as a prison. The museum has 18 permanent and five temporary exhibition galleries with an auditorium for 130 people. The old prison cells were fitted out as offices, laboratories and workshops, while the ground floor has exhibition galleries where we can see the thickness of the stone walls, the original bars or grilles, the narrow doors and cells with vaulted roofs which today serve as the backdrop for the museum’s permanent exhibition.