Juana Bautista de Candelaria Rodriguez, one of the oldest people in the world, smiles to greet visitors.

While some search for the fountain of youth, others are content to simply live long and prosper. But prospering can mean different things to different people.

A new documentary, WALTER, explores what living well means to the people who have lived the longest. Filmmaker Hunter Weeks and his fiancé Sarah Marshall captured their journeys to meet the world's oldest people and find out how they've lived such long, happy lives. While Mary Tankursley, 110, said she had no idea what the key was, others offered up hard-earned wisdom gleaned from seeing the turns of two centuries.

Though her age is unconfirmed, Juana Bautista de Candelaria Rodriguez, a 126-year-old Cuban woman, laid it out in simple terms: "My whole life, I've always been a good person. I've always done good for people, so people do good for me."

Walter Breuning, the film's namesake and the World's Oldest Man at 114, echoed that sentiment: "Helping people — that's the best thing in the world for you. If you could help people, you're doing a good thing for yourself, too."

WALTER opens in New York City on October 4 and Los Angeles on October 11.