The Theme Space under the space frame was divided into three levels, each designed by the artist Tarō Okamoto, The underground level represented the past and was a symbol of the source of humanity. The surface level represented the present, symbolising the dynamism of human interaction. The space frame represented the future and a world where humanity and technology would be joined. Tange envisioned that the exhibition for the future would be like an aerial city and he asked Fumihiko Maki, Noboru Kawazoe, Koji Kamiya and Noriaki Kurokawa to design it. The Theme Space was also punctuated by three towers: the Tower of the Sun, the Tower of Maternity and the Tower of Youth.[5]