75 Upper Alabama St., SW 404 525 2825
It's actually IN Underground, not on top.
Underground Atlanta is on Peachtree Street across from 5 Points MARTA station, but there is an entrance from MARTA that goes right into UG..got down about 200 feet and Mick's is on the Left..kinda at an "intersection".
http://www.underatl.com/1.dining.html