Tatlin’s Tower was a grand monumental building envisioned and blueprinted by the Russian artist and architect Vladimir Tatlin, but never built. It was supposed to be erected in Petrograd after the Bolshevik Revolution of 1917, as the headquarters and monument of the Comintern (the third international). Its proper name was to be The Monument to the Third International.
Tatlin's Constructivist tower was to be built from industrial materials: iron, glass and steel. In materials, shape, and function, it was envisioned as a towering symbol of modernity. It would have dwarfed the Eiffel Tower in Paris. The tower's main form was a twin helix which spiraled up to 400 m in height, which visitors would be transported around with the aid of various mechanical devices.
The main framework would contain four large suspended geometric structures. These structures would rotate at different rates of speed. At the base of the structure was a cube which was designed as a venue for lectures, conferences and legislative meetings, and this would complete a rotation in the span of one year. Above the cube would be a smaller pyramid housing executive activities and completing a rotation once a month. Further up would be a cylinder, which was to house an information (propaganda) centre, issuing news bulletins and manifestos via telegraph, radio and loudspeaker, and would complete a rotation once a day. At the top, there would be a hemisphere for radio equipment. There were also plans to install a gigantic open-air screen on the cylinder, and a further projector which would be able to cast messages across the clouds on any overcast day.
The Monument is generally considered to be the defining expression of architectural constructivism, rather than a buildable project. Even if the gigantic amount of required steel had been available in revolutionary Russia, in the context of housing shortages and political turmoil, there are serious doubts about its structural practicality.
There has been an attempt to build the project, however by building it in parts each of which would be located in a different part of the world, rather than it being one single monument.
(Information comes courtesy of the Wikipedia amongst other sources.)