Artistic and cinematic representations of Christ's crucifixion usually show him on a very tall cross from which he gazes down upon assembled onlookers. In all likelihood, the cross used in his execution was only slightly taller than a man.
The reasons for this were both practical and functional. First, two executioners were able to lift the patibulum and attached victim onto the stipes without need for special equipment. Secondly, it would put the condemned person at a nearly face-to-face level with mocking onlookers and would expose him to predation by wild dogs or other roaming animals.