Superman and Superman II filming locations

[Knocks]

Hi. Was the scene at Lois Lane's apartment filmed at a real rooftop? Seems pretty real with the final shot zooming out and Luis standing there.

Also, in Superman II, were the action scenes at a traffic intersection toward the end of the movie filmed in Manhattan, or was this on a set? Sometimes the shops look real and other times they look artificial.

Niagara Falls also looked real to me. Oh, and what about the "North Pole" location--was any of that real snow?