I don't know dude, I still think he's in a dream. Here's why. Maybe, maybe not. All that Cobb would have to restructure is the airport and the drive back to his home. He's in a plane already, so he exits the plane. I would argue that an airport is an ambiguous enough building that Cobb could easily picture one. It doesn't have to be exact, and theoretically, if Cobb's never been to the airport before, how would he know it's not real? And if he has been there, it's part of his memory, just like the drive home, and able to easily be reconstructed. Cobb gets his stuff, gets in a car, and arrives home. Given what we've seen of the movie up to that point, I can buy that, and it's far from reconstructing the entire real world. And as the corollary to this: But what is Cobb actually constructing? He's not constructing the plane, that comes from memory. We can reasonably assume that he's not constructing the area around his home, seeing as he used to live there and is likely familiar with the area. I still think it's plausible, but that's debatable, and I'm not familiar enough with the movie to be certain. The first option is that Cobb let his father drive him home and didn't pay that much attention to the world outside. It wouldn't even have to be accurate or inaccurate -- Cobb is thinking about seeing his children and is absorbed in his dream. He doesn't care whether or not that building on 34th and Randolph St. is perfect. And because he doesn't pay attention to the details, nothing seems amiss. My argument on this would be that Cobb's projections showed no sign of being perfect. The only thing he would have to recreate was their physical appearances, which, going by the rules of the movie, is absolutely plausible. They never said a word to Cobb at the end. Saito just made a phone call, one that Cobb has likely been thinking about for a long time. I don't think Cobb is in limbo when he finds his kids. I believe he thinks he wakes up, but goes back to a different, previous level of dreaming. I think, though am not sure, this is possible because of how disconnected limbo is supposed to be. It's a shared dreamstate.