The history of Dutch trade unions may not seem especially scintillating, but its famed architect, H.P. Berlage, considered this building, De Burcht (The Citadel), his most successful work. Built in 1900 for the country's first modern labor collective, the Diamond Workers Union, Berlage incorporated his strong socialist principles into the essential structure. Climb the tower for a view of the neighborhood and enjoy a small display of Berlage's fine architectural blueprints
while you're up there. In the various meeting rooms, note the fantastic murals by Richard and Henriette Roland Holst representing the past, present, and future of socialism, stained glass depicting the workers' battle, and the decorative details that fuse Jugendstil with Arts and Crafts stylings on ceilings, doors, and walls. The excellent collection of posters shows the graphic influence of the Soviet avant-garde on designs of the time. Currently being restored, it is due to reopen at the end of 2010.