An exhibition that presents Yves Klein's work in the light of his conception of nature and the cosmos that link man to the earth and the sky. The four elements (earth, water, air and fire) meet and intersect in many of his creations. The Cosmogonies, the Fire Paintings, the Colored Fire Paintings, the Monogolds, the Monochromes, and certain immaterial works show traces of water, burns, body and plant imprints: "the spiritual mark of momentary states". With his Planetary Reliefs, Yves Klein refers to the earth and the infinite, recalling our links with the planets and space. With the Air Architecture, his ultimate project, he proposes the utopia of building cities "with the three classical elements, fire, air and water, the classical city of tomorrow will be built and it will finally be flexible, spiritual and immaterial". With the help of his monochrome colours, Yves Klein reveals the traces of the natural elements, records their presence and extracts the "spiritual principle" from them. Around sixty works, a collection of documents and films on Yves Klein's various exhibitions will be presented for this new proposal. A rare opportunity to discover, through a transversal and thematic vision, the work of Yves Klein who appears today as one of the precursors of Land art, Arte povera and Conceptual art.