For those that may travel to Atlanta for business, or pleasure, I have to recommend dining at the Sundial, which is at the top of the Westin Peachtree Plaza. Take the external glass elevator to the top for a spectacular view. The restaurant slowly rotates 360 degrees while you dine, so you get to see the entire city from 723 feet. Go for lunch on a clear day for a great panorama of the city, and go back at sunset for dinner.
Disclaimer: If you are deathly afraid of heights, I do NOT recommend taking the external glass elevator. It will take your breath away.