I'm so glad this thread was revived this week --
Somewhere In Time is one of my all-time favorite romantic films but I haven't watched it in years. Time to put it on my Netflix queue; we only have it in VHS.
The gazebo in the film is available for weddings, with an indoor chapel as a backup in case of bad weather:
................ 
"The Somewhere in Time Gazebo is situated on a wooded bluff just east of Fort Mackinac, overlooking the lilacs of Marquette Park, the village of Mackinac Island, and Straits of Mackinac. This is the original gazebo from the 1980 romantic movie
Somewhere in Time, filmed on Mackinac Island.
"
Somewhere in Time, the romantic period drama starring Jane Seymour and Christopher Reeve, was filmed on Mackinac Island in 1979 and released in 1980. The film was met with limited interest when first released, but over time has developed a broad following of fans and is now considered a cult classic. Members of INSITE (the
Somewhere in Time fan club) gather for an annual weekend celebration at Grand Hotel on Mackinac Island in October. A monument ("Is it you?") marks the spot where Christopher Reeve's character finds Seymour on the west side of the island.
"The gazebo constructed for and used in scenes in the movie remained on the island after filming. It was placed in the back yard of the Michigan Governor's Summer Residence until the fall of 2005. The gazebo has been restored and moved to a new location on a wooded bluff near Fort Mackinac."
more information, including fees, at
http://www.mackinacparks.com/weddings/index.aspx?l=0,1,6,271