A roller coaster inversion is a roller coaster element in which the track turns riders upside-down and then returns them to an upright position. Early forms of inversions, dating as far back as 1848 on the Centrifugal Railway in Paris, were vertical loops that were circular in nature. They produced massive g-force that was often dangerous to riders, and as a result, the element eventually became non-existent with the last rides to feature the looping inversions being dismantled during the Great Depression. In 1975, designers from Arrow Dynamics developed the corkscrew, reviving interest in the inversion during the modern age of steel roller coasters. Since then, the element have evolved from simple corkscrews and vertical loops to more complex inversions such Immelmann loops and cobra rolls. Featuring fourteen inversions, The Smiler at Alton Towers holds the world record for the number of inversions on a roller coaster.