Everything.

[ Sorry. There wasn't just one thing when none of it was familiar. ]

Water runs through pipes through the whole house, not just a pump you might be lucky enough to have. You find indoor markets everywhere, and the transportation here is beyond expectation or belief. Everything's loud, everything's fast, and people mock you for not understanding what they've known inherently from growing up in this culture. I don't mind that so much... but standing back, learning from what you observe, it's much more difficult than back home.