After winning a race, or coming in the top three, you can control the replay camera and see the track from all sorts of angles.
After your times and scores dissapear, press and hold the B button. This will lock the camera on your player. Now using the control pad, hit either up, down, left or right to rotate the camera or move it high obove your character.
If you make the camera go as high as possible, you get a great view of the tracks you're on!