The Communist regime of the Soviet Union used art and architecture as propaganda. Both buildings and monuments were massive, efficient, and futuristic, an homage to the glorious future of an egalitarian industrial society. To outsiders, the architecture looked grim and menacing, and the style came to be known as Brutalist. The new book Brutal Bloc Postcards is full of, well, postcards of those buildings and monuments, because the Soviets wanted all citizens to be inspired by their grandeur.
Perhaps the most influential architect of the era was a Swiss Modernist named Le Corbusier. Though his romance with the Soviet regime was brief—Le Corbusier only worked with the Russians from 1928 to 1932—the architect left a lasting impact on Soviet Constructivists like Moisei Ginzburg (the author of Style and Epoch) and made poured concrete the material du jour for Russian Modernists. Interestingly, libertarian icon Ayn Rand, for all her open hatred of the Soviets, seemed to love the austere, functional, and material-focused architecture of Le Corbusier and the Constructivists. In her 1943 novel, The Fountainhead, architect Howard Roark and his affection for concrete bears even more similarities to Le Corbusier than his supposed inspiration, American designer Frank Lloyd Wright.
Strangely, the Brutalist style was abandoned during the Stalin era and brought back with Kruschchev. Now many of the Soviet monuments are falling into ruin, but you can read about them and see a gallery of images at Collectors Weekly.