Hi Cris,
This is the first time that I have to deal with such a large terrain data 4.9 million m2 using CAD - 3D MAX. The terrain is really steep with lots of peaks. The CAD file I have is topo lines in 3D space The final product that I have to create is a highly detailed terrain with every tree, pond and rock on it (yes, there is data about trees, rocks, ponds etc.).
Basically, you gave me the direction that I have to start with - Civil 3D or InfraWorks.
Thank you.