Plot:

All that is known, as of now, is that it has been described as a "contemporary sci-fi action thriller set within the architecture of the mind."

Facts:

• Ellen Page, Cillian Murphy, Tom Hardy and Ken Watanabe received private on-hill instruction in Nakiska, Canada because Christopher Nolan wanted them to learn to ski and make real turns, instead of relying on stunt people for the snow scenes. (Source: calgaryherald.com)
• Leonardo Di-Caprio only needed very little ski coaching (Source: calgaryherald.com)
• The production spanned four continents and six countries overall (Source: nolanfans.com)

Quotes:

• “It’s about a five month shoot. We’re having a blast. We’ve shot in a lot of different places so it kind of feels like…you know you do your England leg and then your France and then we were in Morocco and now we’re in L.A. It is a blast and I’m having so much fun. Working with Chris Nolan is a dream. He’s amazing to work with and a lovely guy. There is no ego at all. He’s just a filmmaker. You know what I mean. And that is totally obvious in his films. He’s an incredible filmmaker…but working with him is such a pleasure and often me and the other cast members will reflect on just how excited we are just to be in his movie. I feel like a little kid.”
  (Ellen Page on director Christopher Nolan and the shoot; Source: collider.com)
   
• "It's more of  a science-fiction psychological kind of thriller… It has a heist genre to it, but it’s set within the human mind. It’s one of those movies that I wouldn’t be able to describe if I sat here for 20 minutes because it works on a lot of different… I hate to use that term, again, but it’s true, this film literally works on different levels.”
  (Leonardo DiCaprio on the movie; Source: totalfilm.com)
   
• "It's so great. I am just really honoured and grateful to be working for Mr Nolan. He has such integrity and what's really cool about Inception is that he's getting to make this enormous movie that's just his own brainchild, just his own idea that he wrote out of his head. [...] It's really important to Chris that nothing about the specifics about the story are revealed before people get to see the movie." (Joseph Gordon-Levitt on Christopher Nolan; Source: google.com)
   
• "I've looked up to Leonardo DiCaprio ever since I was very little. He was an actor at a young age, always doing it with such integrity and sincerity. So much of what happens in Hollywood is for all the wrong reasons. That guy does it because he loves it and believes in the art and the craft of it, which shows in his work and his choices. It's something I have always aspired to and to get to work with him and be in scenes with him is really special."
  (Joseph Gordon-Levitt on his adoration for co-star Leonardo DiCaprio; Source: google.com)
   
• "She's a tremendous athlete, and an amazing person to hang with.” (professional ski coach Matt Mosteller on the training with Ellen Page; Source: calgaryherald.com)
   
• "He was the most determined on the fitness side. He wanted to practise all the time." (professional ski coach Matt Mosteller on the training with Tom Hardy; Source: calgaryherald.com)