However numerous architectural elements of the abbot and guest houses had been integrated in the new buildings. During World War I and World War II the citadel was used as prisoner-of-war camp (Oflag XII-B). According to the Treaty of Versailles in 1919 - and the slighting of the fortifications in and around Mainz as effect of it- the military history of the citadel of Mainz ended. Nevertheless, during the last days of World War II, the population of Mainz took shelter in the casemates of bastion Drusus, which had been turned into air raid shelters. After World War II After the Second World War the French army seized the premises until 1955. The Paul Tirard School, named after the chair of the Inter-Allied Rhineland High Commission (1919–1930), was opened by the French administration in 1950 for education of the children of French military and civilian personnel civil during the occupation. The citadel today Today the citadel is owned by the city of Mainz and accommodates numerous municipal offices. Mainz Citadel has been administered as part of the city's cultural heritage since 1907. The trench in the southern part of the citadel had been considered part of the city's natural heritage since the 1980s. One of the buildings near the Drususstein today houses the Mainz historical museum. The citadel and its surroundings bear witness to the entire history of Mainz concentrated in one spot, going from the Roman cenotaph, the Drususstein (Drusus monument) via the fortress barracks and up to the World War II air raid shelters. Since 1975, an annual youth festival, the Open-Ohr festival, has taken place at the citadel during Pentecost weekend. See also List of forts Petersberg Citadel Salomon Gluck External links (de) www.festung-mainz.de/zitadelle Initiative Zitadelle Mainz e.V. Stadthistorisches Museum auf der Zitadelle References Forts in Germany Castles in Rhineland-Palatinate Zitadelle Mainz Zitadelle Mainz Tourist attractions in Rhineland-Palatinate Museums in Rhineland-Palatinate Local museums in Germany Military and war museums in Germany