Opened by Mayor Konrad Adenauer, later the first Chancellor of West Germany, in 1924, Koelnmesse's monumental halls and auditoriums, crowned by the tower, are a reflection of the optimism prevalent in the country during the 'Golden Twenties'. Used by the Nazis as a detention center for Jews, Gypsies and political opponents, the exhibition center was destroyed during World War II, but rebuilt shortly after the war came to an end. With 14 halls, Koelnmesse is the fourth largest in the world. Approximately 25 major trade fairs take place here every year. In April, the center hosts Art Cologne (International Art Fair Cologne).