From those travels Clerici developed two themes: the "mirages" and the "temples of the egg", cycles of constructions set in the desert and spiralling from a central core containing a hypothetical primordial egg. In parallel to his paintings, which became more and more fantastic and magical, he worked for the theatre. On this return from Egypt he created sets for "La vedova scaltra" by Carlo Goldoni under the direction of Giorgio Strehler. Before that he had produced the sets of a number of ballets and lyric works, always with the theme of a fantastic world. He then made the sets and costumes for Igor Stravinsky's ballet "Orpheus", presented at the La Fenice theatre in Venice in 1948; for "Dido and Aeneas" by Henry Purcell and for "The Rape of Lucretia" by Benjamin Britten, both at the Teatro dell'Opera di Roma and directed by Alberto Lattuada (1949); for "Armide" by Jean-Baptiste Lully (1950); for the comic opera "Gianni Schicchi" by Giacomo Puccini, directed by Peter Ustinov at the Royal Opera House in Covent Garden (1962); and for "Ali Baba" by Luigi Cherubini, at the La Scala in Milan. Over a two-year period he helped create the big stained glass window "La fede di Santa Caterina" for the Basilica of San Domenico in Siena (1957). In 1964 he began a series of tables for "Orlando furioso" of Ludovico Ariosto. In 1968, on the occasion of the Berliner Festspiele, he participated in two exhibitions on painting and scenography in the "Neue Nationalgalerie" and the "Galerie im Rathaus Tempelhof". In 1970 he produced for Berlin's "Propyläen Verlag" an edition of "The Travels of Marco Polo" ("Il Milione") of Marco Polo, with tables and original lithographs. The drawings were exhibited with other paintings at the "Galerie Brusberg" in Hanover (1971). In 1974-75 he painted a cycle around the theme "Isle of the Dead of Arnold Böcklin. In 1977 he made a series of lithographs for an edition of "Le bestiaire" by Guillaume Apollinaire. During the same year three important retrospective exhibitions were dedicated to Clerici at the Museum of Western and Oriental Art in Kiev, the Fine Arts Museum in Almaty and the Pushkin Museum in Moscow.