Calidoscopio became the oldest ever winner of a Breeders' Cup race when landing the 2012 Marathon at the age of nine.
- Related Content
The South American stayer powered down the home stretch under Aaron Gryder as favourite Atigun began to tread water having led down the far side.
Grassy came through to claim second ahead of the market leader but from the furlong marker this was a one horse race.
Juniper Pass ran a good race under Frankie Dettori to finish fourth.
Fame And Glory was a huge disappointment, dropping himself out turning away for the second circuit and finishing tailed off alongside fellow Irish raider Sense Of Purpose.
Grydon said: "It's been a privilege to get on this horse. These people were great to bring this horse in and kept him for this race."
The winning trainer said: "I'm so grateful we got the invitation to run in the Breeders' Cup Marathon and this is for all the people who have helped me."
Trainer Aidan O'Brien revealed that Fame And Glory, winner of the 2011 Gold Cup at Royal Ascot, has been retired.
He said: "The race was there in the book and we gave it a try. We took a chance and it didn't come off, so he will be retired now. He just showed us that he didn't like it and he wanted to go home."
The six-year-old's jockey Jamie Spencer said: "I was exactly where I wanted to be in the stretch first time, but then all of a sudden he just didn't want to know."
Sense Of Purpose's trainer Dermot Weld said: "My mare didn't handle it and that's it. There's nothing you can do. She didn't like the dirt coming up into her face."