Built in 1883 by railroad baron James J. Hill the Stone Arch Bridge is the only bridge of its kind spanning the Mississippi River. Built of native granite and limestone it measures 2,176 feet long by 28 feet wide, and is comprised of 23 arches. A working railroad bridge until 1965 today it serves as a pedestrian and bicycle bridge, and provides some of the most stunning views of the Mississippi River and Saint Anthony Falls. Saint Anthony Falls is located northeast of downtown Minneapolis and was the only natural major waterfall on the Upper Mississippi River. The natural falls was replaced by a concrete overflow spillway (also called an "apron") after it partially collapsed in 1869. Named after the Catholic saint Anthony of Padua, the falls is the birthplace of the former city of St. Anthony and to Minneapolis when the two cities joined in 1872 to fully utilize its economic power for milling operations. From 1880 to about 1930, Minneapolis was the "Flour Milling Capital of the World." The Mill City Museum, housed in the ruins of the former Washburn "A" Mill, is just downstream and overlooks the falls as does the Stone Arch Bridge. Gold Medal Park served as a memorial site for the victims of the I-35 Bridge Disaster as it overlooks the site of the disaster. It is also a 7.5-acre park next to the Guthrie Theater in Minneapolis, Minnesota. Designed by landscape architect, Tom Oslund the park opened in May of 2007. It takes its inspiration from the Dakota Indians burial mounds that are found through Minnesota. It consists of a 32-foot (9.8 m)-high mound, reached by a spiral walkway rising out of a green lawn with 300 trees. The park, just east of the Guthrie Theater, provides the Mills District neighborhood with some rare green space.