Revealing mistake: In the final scene when Annie and Sam are exiting the observation deck coming towards the elevators, the New York skyline backdrop which should be visible behind them is missing, and the entire sound stage wall can be seen beyond the observation deck safety railings instead. 'Although the exterior and lobby of the Empire State Building, 350 Fifth Avenue at 34th Street, are the real thing, a slightly larger replica of the Observation Deck was built in a hangar at Sand Point Naval Base on Puget Sound just northeast of - where else? - Seattle.' https://www.movie-locations.com/movies/s/Sleepless-In-Seattle.php. (01:39:35)
Revealing mistake: Meg Ryan listens to the radio broadcast while driving her car down a highway at night. In the head-on shots of her, you should be able to see in her windshield the reflections of the streetlights as her car passes under them.
Answer: That would be the Rainbow Room which is located at 30 Rockefeller Plaza (Annie rushes out the door and gets into the taxi), the iconic skyscraper in Rockefeller Center.
Super Grover ★