What are the Best places or adventures to do in and around atlanta,GA?

Hi, My frnds are coming to visit me for a long weekend, I stay in Downtown Atlanta, but I am new to ATL as well. I want to show them really good places and take them for adventures like hiking, tubing, rafting etc which are in and around Atlanta. Can you please suggest me some good places or fun activities to do. In consideration with time I can drive up to 100-150 miles (i.e. max of 2.5 to 3 hours of drive) one way. how about some thing like smokey mountains (not sure though)??