A tourist destination for the Midwest , Duluth features America 's only all-freshwater aquarium , the Great Lakes Aquarium ; the Aerial Lift Bridge , which spans the Duluth Ship Canal into the Duluth-Superior Harbor ; and Minnesota Point ( known locally as Park Point ) , one of the world 's longest freshwater baymouth bars , spanning 6 miles ( 9.7 km ) .
Duluth is known for the Aerial Lift Bridge , which spans the Duluth Ship Canal into the Duluth-Superior Harbor .