Monument to the Third International, also sometimes known simply as Tatlin's Tower, is his most famous work, as well as the most important spur to the formation of the Constructivist movement. The Tower, which was never fully realized, was intended to act as a fully functional conference space and propaganda center for the Communist Third International. Its steel spiral frame was to stand at 1,300 feet, making it the tallest structure in the world at the time. It was to be taller, more functional - and therefore more beautiful by Constructivist standards - than the Eiffel Tower. There were to be three glass units, a cube, cylinder, and cone, which would provide functional space for meetings and would rotate once per year, month, and day, respectively. For Tatlin, steel and glass were the essential materials of modern construction. They symbolized industry, technology, and the machine age, and the constant motion of the geometrically shaped units embodied the dynamism of modernity.