At the “lookout” in Bracknell. Bracknell gets a bad press, and the center is indeed horrible, but it has nice paths for walkers and quite a decent bit of woodland. Where I saw my first ever mountain-bike unicycle. I didn’t see anyone riding it, but they did have a lot of pads.
Inside, they had this rather nice fluid-dynamics toy: a perspex cylinder about 1/2m wide and 2m high, with a circulation about the vertical axis imposed by the water flowing in at the top. And a valve you could turn, that did something slightly unspecified, but which we’re fairly sure was to change the speed of outflow from an approx 1″ dia plughole in the center at the bottom. Which lead to the effect you see in the pic, of a very long thin tube of air reaching down to the bottom, much like a tornado. Note the interesting corkscrew patterns imposed on the sidewalls of the tube; those were quite stable, and didn’t turn. A coriolis effect thing; but of course they didn’t explain it.
It takes more than good intentions / And a big bloke on the door / And though it’s never the same after the first time / That doesn’t stop them coming back for more