Uncle Tom's Cabin Scene
It just doesn't get much better than this scene. The dancing and choreography are just so spectacular to watch. The music and descant voices just add to the story telling.
Of course the portrayal of Asians in this movie (specifically Thai people) is seriously dated and offensive, but even this is not enough to deter the viewer from appreciating the overwhelming mastery of music and dance exhibited by Robbins, Rodgers and Hammerstein.