Meramec Caverns
Sullivan, MO · Missouri Ozarks$$
Cut into the Ozark hills outside Sullivan, Meramec Caverns runs more than four and a half miles through seven levels of limestone, and the formations earn the billboards: the…

Photo: w_lemay / CC BY-SA 2.0 · source
Eero Saarinen's 630-foot stainless-steel arch stands on about 91 acres of St. Louis riverfront, the smallest national park in the system. A tram climbs up inside one leg to a deck at the top, with the Mississippi on one side and the city on the other. The museum on westward expansion sits underneath.
Gateway Arch National Park, 11 North 4th Street, St. Louis, MO 63102