Out of all the different civilizations, which one is the least known ?

Question

Since you're asking about the "least known" civilization, there aren't going to be many (if any) answers -- since people don't know about it!

If you search Google for "little known civilizations" (including the quotation marks), here are the results:

http://www.google.com/search?q=%22little+known+civilization%22&rls=com.microsoft:en-us:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7SUNA

=)