Toroidal vortices, abstract and real-- I hadn't thought about generalizing smoke rings.
World's largest rope swing: physical exuberance for adults
Suppose you had two giant animatronic cranes with great big video screens on their bellies....
Links from elenbarathi here, plus a few more videos.
This entry was posted at http://nancylebov.dreamwidth.org/558664.html. Comments are welcome here or there. comments so far on that entry.