From Curbed:
Barton Hall, a National Historic Landmark in Cherokee, Alabama described by the National Park Service as an "unusually sophisticated Greek Revival-style plantation house," is on the market for $1.75 million. And, no big deal, but it happens to include one of your standard double reverse spiral staircases, which makes it look like an MC Escher print come to life.
Chambord of course famous for its double helix staircase (well that and the roof and the 400+ rooms and the 13,000 acre park and the 200k+ square feet [or 400k, no one's really sure] and the lack of comparables and...):
