Cai Guo-Qiang, who had been staying in Japan since 1987, gained attention with open-air works using gunpowder explosion which he successively presented in several cities of Japan, and is now one of the Asian artists most highly appraised in the Western art world. This work is a plan-drawing for his work intended for the first ‘Museum City Tenjin’ in 1990, a contemporary art exhibition using the urban space of Fukuoka. It illustrates his project to produce the so-called ‘mystery circles,’ which were regarded as traces of the landing of UFOs found in various parts of Japan at that time, in a roof-top heliport of a city building, by means of exploding gunpowder. Although this plan was not realized, this is a valuable example of the early works of this artist, who is characterized by his grand thoughts in terms of interest in the history of civilization on a global scale and by the spectacles that he produces with gunpowder, which is an invention of the Chinese. The title ‘Tenjin’ refers to the name of the central district of Fukuoka City, and literally means ‘god of heaven.’