When architect Eero Saarinen designed the iconic Gateway Arch in St. Louis, he created a stunning 630-foot catenary curve. But there was a glaring problem: nobody knew how to get visitors to the top.
Standard vertical elevators were useless because the arch curved sharply outward and tapered from a 54-foot triangle at the base to a mere 17-foot triangle at the apex. Traditional inclined elevators couldn't handle the constantly shifting angle, which changes dramatically from vertical to almost horizontal near the top. Major elevator companies gave up, but Saarinen turned to Dick Towler, a college dropout and elevator designer.
Towler spent just two weeks conceiving a revolutionary hybrid system. He combined the mechanics of an elevator, a train, and a Ferris wheel. The system uses a train of eight barrel-shaped, five-passenger pods linked together inside the hollow steel legs.
As the tram ascends along curved tracks, electric motors continuously rotate each individual pod by 180 degrees over the course of the journey. This gimballed auto-leveling keeps passengers sitting upright the entire time; without it, riders would end up tilted sideways or completely upside down. Operating reliably since 1967, the Gateway Arch tram remains one of the most custom-engineered, mind-bending passenger transit systems on the planet.