Fred Astaire's famous dance from Royal Wedding (1951)

Demystified:

And explained:

But the more you think about it, the more amazing an accomplishment this number seems. The cage must have had a diameter of something like 20 feet, and the light fixtures had to stay powered throughout. The whole thing must have weighed a ton or two. Building this set was an enormous feat of engineering. What would it look like to a bystander as this amazing scene was shot?

Movie buffs will want to continue reading the explanation here.