Okay think of it this way;
Railroad. Draisine. We've all seen these things.
Riding Horses. We've seen those (and potentially eaten them now, too).
Walking/Graal Paced Movement - I'm not sure if we're running, jogging, or quick walking. Either way, we've all seen this.
These are all tangible ways of travel. They make sense.
A slide that "slides across all of Graal" with hop on and drop off points.
I'm fairly certain this would defy gravity and most certainly escapes any logic. A slide goes from up high, to down low. Not up high, across this pond, back up over Graal City, back down again near this land mass, up again, back down, circle, back up a higher mountain than the one you started on (physically impossible) and then...
Get my point?