With the travel award he received in 1957, Darel lived in Europe for two years, but this experience proved distressing, and the desire to return was constant. With experience, he realized that all cities are similar, in the confusion of urban layouts and the labyrinth of information—an excess that paradoxically generates anguish and a profound sense of loneliness.

Upon his return to Brazil, he created "Invented Cities," a recurring theme that he would develop in engraving, lithography, and painting. Regarding this work, Mario Pedrosa said:

"The line is not there to be read, but to invoke, to evoke an inner vision, which lies behind appearances. This is a beautiful function of his drawing, which, despite being structured and constructive, invites us to penetrate appearances in search of the heart of things. In a Brazil of superficial illustrative artists or of abstract or inane vagueness, the lesson of Darel's substantial drawing is invaluable."