"The gigantic Hercules leaning on his club had been found in a well more than forty years before Goltzius went to Rome: first the head and then, six years later, the bowed body. The statue had an enormous impact and was immediately appropriated by the Farnese family. ...it is now thought that it is an enlarged copy made by this sculptor [Glycon] in the early third century of an original by Lysippos or someone of his school. Because of its great height (som 3.10 metres,...) it can only be viewed and drawn from some distance away... Although Goltzius also drew a front view, he was well aware that the back would make a much more compelling print, and so devoted himself to meticulous preparation of the print model for it... Goltzius selected a vantage point from where the heels of the colossus do not quite overlap and the top of the back and the arms form a semi-circle... Goltzius did not make things easy for himself; he choose to depict the statue against the light, and to make lavish use of white highlights... [he] did not define the exact shape of the club, draped with a lion's skin; he did, however, devote a great deal of attention to the muscles of the right arm, ending in the hand that holds the three captured golden apples of the Hesperides.
The two onlookers... give us a sense of the scale of the statue. They also reinforce the effect described by Pliny: the two see the chest and the face of the colossus that we can only imagine from our rear vantage point, and this lends the print an agreeable tension." Leeflang & Luijten, p. 133-134.