Situated in the Citadel in Victoria, Gozo the Old Prison lies adjacent to the Courts of Justice to which it was originally connected. In its present form, the prison complex is divided into two sections: the entrance hall which served as a common cell in the 19th century and now hosts a permanent exhibition on fortifications and a free-standing block with six individual cells. Having undergone a number of structural modifications, this prison was in use from the mid-16th century until the beginning of the 20th century. Soon after their arrival in Malta, the Knights of St John used this prison to intern their rowdy and disruptive members. The list of notorious inmates included Fra Jean Parisot de La Valette (later, Grand Master of Malta) who, in 1538, spent four months in the Gozo prison after having attacked a man.

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After the expulsion of the Knights of St John from Malta, the prison remained in use. From the mid-19th century, another building on the other side of the Citadel started functioning as a prison and continued to serve this purpose until it closed down in 1962. Initially, the new prison was in use simultaneously with the old one which, for some decades, continued to house those individuals awaiting trial. The walls of the cells and corridors in the Old Prison are covered with graffiti. This is the largest known collection of historical graffiti in one single place on the Maltese Islands. They include mainly sea vessels and date from different periods. But there are also palm-prints, crosses, names, dates, games, and anthropomorphic figures. Some inmates also appear to have scratched a tally of their length of stay behind bars. These graffiti provide a fascinating insight into the lives of those incarcerated here.