Russian artist and designer El Lissitzky was one of the leaders of the avant-garde art movement at the birth of the Soviet Union. But its one of Lissitzkys unrealized concepts that proves the most enduring: his horizontal skyscrapers. Now architect Guillaume Mazars has imagined a way these unbuilt structures could be built with his concept Reveal the absence, the un-built. The buildings — called Wolkenbügel, or cloud irons — were put forward by Lissitzky as a more natural alternative to typical Western skyscrapers. It would, Mazars says, reconstruct the spatial presence of [the] El Lissitzky project without physically reconstructing it, so the imaginary project remains invisible but perceptible.