For natural (as a landscape architecture major, I'm against using of "natural" term), I would choose the Yellowstone NP, Wyoming. The spot would be the West Thumb, in Lake Country (where the Fisherman's Cone is).
For manmade, well, I would choose the Chicago's Michigan Ave. The spot would be by the Michigan Ave's bridge, sitting in the Chicago Tribune Courtyard and looking at the Wrigley's Building. Awesome site!
FYI: Chicago Tribune was designed by Greek - Raymond Hood
GO GREEK!