El Lissitzky designed Cloud Iron, Wolkenbugel in 1925. It comprised of identical horizontal skyscrapers featuring a precarious cantilever. The series of eight such structures was intended to mark the major intersections of the Boulevard Ring in Moscow. Each Wolkenbugel was a flat three-story, 180-meter-wide L-shaped slab raised 50 meters above street level. It rested on three pylons (10×16×50 meters each), placed on three different street corners. One pylon extended underground, doubling as the staircase into a proposed subway station; two others provided shelter for ground-level tram stations.
Lissitzky argued that as long as humans cannot fly, moving horizontally is natural and moving vertically is not. Thus, where there is not sufficient land for construction, a new plane created in the air at medium altitude should be preferred to an skyscraper tower. These buildings, according to Lissitzky, also provided superior insulation and ventilation for their inhabitants. Lissitzky, aware of severe mismatch between his ideas and the existing urban landscape, experimented with different configurations of the horizontal surface and height-to-width ratios so that the structure appeared balanced visually ("spatial balance is in the contrast of vertical and horizontal tensions"). The raised platform was shaped in a way that each of its four facets looked distinctly different. Each tower faced the Kremlin with the same facet, providing a pointing arrow to pedestrians on the streets. All eight buildings were planned identically, so Lissitzky proposed color-coding them for easier orientation.
As in many of his other works, which spanned vastly different media, the Wolkenbugel underscores Lissitzky's belief in the beauty of industrial production and a desire for pure monuments of technological progress. Cloud Iron has become famous for its structural daring and futurist aesthetic. Lissitzky's towers have enjoyed a long afterlife, with many projects from the twentieth century, borrowing Lissitzky's design.