Forks of the Credit Provincial Park is Caledon's best all-round nature stop. Trails cross forest, river valley, and Niagara Escarpment terrain, with enough variety for a real half-day walk rather than a token stroll.
The park also has human traces: old mill and dam ruins visible from the trail system. It is especially good in autumn, but weekends can be busy and parking rules are worth checking before you set out.