Siblings and I did that as kids. Not only that, but our parents enabled it. Every time we drove home from a visit to Disneyland-area amusement zones (Knotts Berry Farm, The Alligator Farm, etc) Dad stopped at a public park with a high, grassy hill and we kids repeatedly rolled down, trudged back up, and rolled down again, all for the chlorophyll and dizziness high. Look at us now, confirmed chlorophyll junkies. Nice going, folks. 
I recall us given reptilian rides at The Alligator Farm. Maybe the hillside high was to help us recover from the terror.
