Zardoz

In the distant future Earth is divided into two camps, the barely civilized group and the overly civilized one with mental powers. One day a barbarian, Zed, stows away in the giant head that supplies the barbarians with munitions and food and that his people worship. When the head returns to its station in a lush city, the barbarian finds himself surrounded by the telekinetic ruling class of "Homo Eternals".