Centered around St. Anthony Falls, the multi-use district contains fascinating relics of Minneapolis' earliest industry. Soldiers at Fort Snelling built the first mills on the falls in the early 19C. By the 1880s, some two dozen gargantuan flour mills lined a three-block corridor surrounding the falls, and warehouses cropped up nearby. Recent gentrification has turned some of the old brick buildings into bars, restaurants and loft apartments. St. Anthony Falls Heritage trail (pedestrian and bicycle traffic only) loops for 2mi along the riverfront and passes two important landmarks: the 1881 blue limestone Pillsbury "A" Mill (not open to the public), the largest flour mill in the world at the time of its opening; and the 1883 Stone Arch Bridge. Celebrated as an engineering marvel, the curving, 2,100ft-long span is the only stone bridge to cross the Mississippi River.