\"Tour the world's biggest and busiest locking system, located on the American/Canadian border at Sault Ste. Marie, Michigan,\" just 50 minutes north of the world's largest suspension bridge between cable anchorages, the Mackinac Bridge; via Soo Locks Train Tours. Climbing 135 feet above this gigantic lock system, this historic tour passes through Sault Ste. Marie, Michigan and crosses the 2.5- mile long International Bridge into Sault Ste. Marie, Ontario.