Trivia: In the part of the movie that begins with Valentine's Day, there's a shot of a store with a heart (and other Valentine's decorations) in the window. Pasted on the heart is a black silhouette of a man and woman looking into each other's eyes. If you look closely, you'll notice the silhouette is of Tom Hanks and Meg Ryan.
Trivia: Dyan Cannon, who is mentioned in the film and was married to Cary Grant (who is also mentioned in the movie), grew up in Seattle - West Seattle, specifically. The large house where many interior shots were filmed is in the West Seattle neighborhood (where I live) on Sunset Drive. This house is less than two blocks down the same street from where Dyan Cannon's father was living at the time.
Answer: That would be the Rainbow Room which is located at 30 Rockefeller Plaza, the iconic skyscraper in Rockefeller Center.
Super Grover