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)
