Here's the one Colin Furze built a couple years ago in his workshop. He only took it down a few weeks ago to reclaim the space.

There's also an older one on his channel that he built over 17 years ago, out of pallets in a field.

Its like a big walled circle and they ride motorcycles, bicycles, go karts etc around on the wall, you can reach down with tips and they reach up and grab the money from you as they ride along, they are basically horizontal as they are riding