We stumbled on this fun trail completely by accident after we attempted to go to the Canyon View Park in Spanish Fork Canyon and found it closed. (We went to Canyon View on another day and all I really have to say about it is - meh.)
It's a wilderness area with a marked trail, that begins with a sort of a treasure map. Along the trail there are discovery/information stations and exhibits. My kids really loved it. Still seems to be a pretty well kept secret. Absolutely free.
Information and directions: