Remember these? They weighed a ton and had an up and down back and forth rocking motion that you could build up to dangerous, violent levels so small children (usually me) would be thrown off onto the concrete floor, or knocked unconscious by the horse itself. Those were the days

My local park also had a barrel you had to try to stay on top of while your mates rotated it. Can't find a picture of this one. I once went home with blood pouring down my face and clothes from a gash on my forehead where I went headfirst over it. I've still got that scar!

This kind of thing, but wooden cylinder rather than barrel-shaped, and steps up each end and solid structure, not pipe / rail. And concrete floor of course.