Tomorrowland's showpiece was the TWA Moonliner, derived from Disney's "Man In Space" television episodes developed in the 1950s. The Moonliner was the tallest structure in the park at the time, even taller than the park icon Sleeping Beauty Castle. The Moonliner hosted Rocket To The Moon which was a ride to the moon. The entrance showpiece was the clock of the world showing the time anywhere on earth. The north show building hosted Circarama U.S.A. which showed movies on nine screens, and space station X-1 which showed a satellite view of America. The south show building showed the Monsanto Hall of Chemistry, which was a walk-through tour about chemistry. Autopia, an opening-day attraction, gave visitors a view of the National Interstate System that was to be built in the future. The attraction still remains open today, though it has been modified and rebuilt several times. This is the only attraction in Tomorrowland that has been open since opening day.