A ride to the top of the 630-foot arch, designed by architect Eero Saarinen, is a must. The centerpiece of the 91-acre Jefferson National Expansion Memorial Park, the arch was built in 1965 to commemorate the city where thousands of 19th-century pioneers stopped for provisions before traveling west. A tram takes visitors up one of the Arch's legs to a top-of-the-arch observation room with a terrific view of the city and the Mississippi. On windy days visitors can feel the Arch sway while at the top. Beneath the Arch is the underground visitor center and the Museum of Westward Expansion.