This building, nicknamed "de Burcht" (the fortress), in reference to its solid exterior which evokes the strength and unity of the trade union, was built by Berlage in 1900 to house the diamond workers' trade union. The interior is laid out around a splendid varnished brick stairwell illuminated by natural light pouring through a glass roof and by a remarkable central lamp which prefigures the Art Deco style. The well of light created by these features symbolises the aspirations of the working class for a better society.