I've driven past this rather unassuming building a billion times or so, not suspecting until recently that it had some historical significance -- it's one of the first (and possibly the first) buildings that famous architect guy I.M. Pei designed in America.
According to the Atlanta Preservation Center (from whence I learned the above), it used to be the Gulf Oil building. So there ya go.
I don't know much about architectural styles, so I can't say much about Pei's style -- I just know he's one of the few architects whose names I recognize. Honestly, the above building isn't that thrilling, but apparently its future is somewhat in doubt -- and undoubtedly whatever might replace it wouldn't have similar historical interest.
Something -- for the life of me I can't think of what was there -- recently was demolished on Peachtree south of 3rd, revealing these old ads on the outside of what used to be Agatha's Mystery Theatre (a sign that I don't get over there much, I guess, is that I didn't realize the latter business had gone under).
This is just north of the old Georgian Terrace Hotel, so long ago, guests such as Warren G. Harding and F. Scott Fitzgerald (according to Wikipedia, at least) might have emerged from the hotel and found themselves tempted by whatever Charles Willis was selling.
(EDIT: I knew I'd seen something else about threats to the Pei building recently -- here. Link via the excellent I Saw It On Ponce.)