They were designed by architect Branko Petričić (1911-1984). He worked with Le Corbusier and accepted his idea of Ville Radieuse, which he applied in the Fontana's design.
The Fontana building was designed by Branko Petričić, who worked alongside Le Corbusier and embraced his vision for Ville Radieuse.  Petričić applied this idea to the design of the Fontana structure.