Now an imposing ruin, the Penitentiary was constructed in 1843 as a flour mill and granary. In 1857 it was converted into a penitentiary, capable of housing over 480 convicts in dormitory accommodation and separate apartments.
Flanked by the Watchmen’s Quarters, the Penitentiary also contained a mess room, library, Catholic chapel, workshops and ablutions complex. The building was gutted by fire in 1897 and lay derelict until a concerted conservation program began in the 1960s.