Directed by Ayan Mukerji, the fantasy adventure series is produced by Karan Johar's Dharma Productions.
Also featuring megastar Amitabh Bachchan, the movie will see Ranbir playing a character with special powers.
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In a recent interview, Ayan told PTI, that his good friend and frequent collaborator Ranbir will undergo training in horse-riding and gymnastics for the film.
"There is lot of action, so there is lot of training, like gymnastics kind of training, horse-riding, fighting and lot of physical stuff that Ranbir will have to do. And then there is internal work, like to get the spirit of the character right.
"Ranbir has to observe the flavour of the film and communicate it with the audience. We are trying to imagine things, this (fantasy) world, and work accordingly," Ayan had said.
The team will start the shooting sometime early next year.