How site sensitive is the site?

If your answer is "slightly more than average", then don't modify it, build next to it.

Also, no trees? 

Traditions:

http://www.nhmagazine.com/July-2013-1/Above-it-All-A-Guide-to-the-White-Mountains-AMC-Huts/

Obviously not the same site constraints.

no trees... the rocky mountain is this .. just to give you an idea 

... I was just wondering if someone know any way to model digitally the non-functional terrain that does not appear on google earth model.....?

Oh. Yeah. I can help.

http://viewer.nationalmap.gov/basic/?basemap=b1&category=histtopo,ustopo&title=Map%20View

Find the 7.5 topo you want. Download the pdf. Open it in CAD or Illustrator. Extract the topo lines. Scale it up. Loft the lines, make the 3d topo.

:) thanks SneakyPete but it seems this website only for National Geo of the US... :)

besides, I can find the iso-hypsis of thos mountain, but don't know how to to model the "nonfunctional terrain" such as existing caves small hills.. the exact curvatures of a specific part of the mountain.. ? 

Check NASA's SRTMs. You can use the data in grasshopper/elk to make surfaces. It likely will not be high resolution, but is a consistent representation. 

And when you say Iso-hypsis, are you referring to contour elevation or barometric pressure? If it is the physical contours you are looking for, the point data in SRTMs are geolocated, so you can use the contour tool in grasshopper or rhino to generate that information where you need it.

Displacement maps in a rendering engine?