thx sandman, I thought that including that reference object would seem like something I just made fit there... I guess a single object would not do it, I need the whole scene for reference.. so I made some sketches and I'm finally getting some results... I will change the whole scene.
Now the reference object is the complete surrounding... and for more clear comparision I guess I'll model a man standing by the obelisc.

Now look at the stairs I dug in the rock.. I think it works..