Caledon is the green, rural edge of the Greater Toronto Area: not one tight town centre, but a spread of villages, farms, conservation lands, and Credit River valleys. The Niagara Escarpment runs through it, which is why the landscape changes so sharply from ordinary commuter country to red badlands, wooded gorges, and small waterfalls.
The best day here is outdoors. Cheltenham Badlands gives the quick visual hit, with its rolling red shale slopes and boardwalk. Forks of the Credit Provincial Park and Belfountain Conservation Area are better for walking, especially if you want the Credit River, forest, and escarpment in one afternoon.
Caledon is close enough to Toronto and Brampton that it can feel like a backyard escape rather than a separate destination. That is part of the point. If you have a car and one free day, it is one of the easier ways to trade traffic and malls for trails, farm roads, and proper countryside.