The Rio 2016 Olympics will be remembered for many things — Katie Ledecky’s dominating performance in the 800-meter freestyle, Simone Biles’s flawless gymnastic routines, Abbey D'Agostino’s and Nikki Hamblin’s sportsmanship during the 5000-meter qualifying run, and the list goes on. However, the moments that will be forever etched on everyone’s minds will be the events that featured two of the world’s greatest athletes — Jamaican sprinter Usain Bolt and American swimmer Michael Phelps — who both declared their retirement following the Rio Games.