 1967 marked the beginning of Piene's involvement with "Sky Art", a term he coined in 1969 for his use of landscape and cities themselves as the focal point of his work.For the closing of the 1972 Summer Olympics in Munich, Piene created the sky work "Olympic Rainbow", made up of five different-colored floating helium-filled polyethylene tubes, each long.Between 1981 and 1986, Piene organized four Sky Art conferences in the US and Europe.