I Wonder

On the MPAA site it lists alternate titles for Prometheus which could have been: [i]"Paradise"[/i] or [i]"Tomb of the Gods"[/i] So perhaps the alternate titles begin to give some clue as to what those constructed mounds are on the planet. Perhaps, as others have said, the giant head is a monument to one of these Engineers who is now dead (aka the Sacrifice Engineer who seeded life on our planet)

Ohhh thats a good deduction, i had'nt thought of that