The name of the exclusive restaurant in the film is "Il Mare". "Il Mare" is also the name of the house and the International title of the Korean film upon which "The Lake House" is based, Il Mare.
Sandra Bullock states that she felt compelled to name the dog "Jack" after the character of Keanu Reeves in Speed - the first movie the two of them made together.
The address of the building in Chicago at which Sandra Bullock lives is 1620 Racine. This would place it in the same block as the apartment belonging to Sean Connery in The Untouchables (Connery's character lived at 1634 Racine).
The lake house measured 2000 square feet and sat on top of steel beams ten feet above the waterline. It used 35 tons of steel and required nearly 100 carpenters, welders and painters to build it.
Simon Wyler's death date is listed as October 6, 2004. October 6 is also the birthday of Swiss architect Le Corbusier, one of the two architects mentioned as his influences when he designed the Lake House (the other is Frank Lloyd Wright).
The actual house did not exist and was built for the movie, then dismantled. In using Google Earth to see the house, enter 41.7142, -87.8901 in the window on the Fly To tab. This will take you to the center of the lake. Zoom to the clearing on the eastern shore. Then select April 29, 2005 as the date.
The location of the lake house, on Maple Lake, is located in the same Forest Preserve and is approximately 1 kilometer away from the site of the world's first nuclear reactor, CP-1, which was constructed during World War II's Manhattan Project in the Forest Preserve.