From Wikipedia:

In a symbolic act, activist Abbie Hoffman vowed to levitate the Pentagon. Hoffman claimed he would employ the use of psychic energy to levitate the Pentagon until it turned orange and begin to vibrate, at which time the war in Vietnam would end. The event was accompanied by Allen Ginsberg leading Tibetan chants to assist Hoffman. While levitation did not occur, the act served as a powerful symbol of the protesters’ opposition to the Vietnam War.