Kristen Stewart and Robert Pattinson are currently in Rio, Brazil, to film the first part of Twilight Breaking Dawn, aka Twilight 4:

Breaking Dawn Movie

(Click on a picture to enlarge it.)

And here’s a spy clip showing Kristen Stewart and Robert Pattinson prepping up for a night scene of the movie Twilight 4 Breaking Dawn:

Behind the Scenes of Twilight 4 Breaking Dawn
Wondering why Bella (Kristen Stewart) and Edward (Robert Pattinson) are in Brazil? Well they went there for their honeymoon!
:)